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The 

California Earthquake 

of 1906 




The Town Columns. 



T h 



v><alif ornia rLarthquake 

of 1906 



Edited by 

David Starr Jordan 

Articles by 

David Starr Jordan John Casper Branner 

President Stanford University Vice-President and Professor of Geology 

at Stanford University 

Charles Derleth, Jr. 

Associate Professor of Structural Engineering, 
University of California 

Grove Karl Gilbert Stephen Taber 

United States Geological Survey Stanford University 

F. Omori, Sc. D., 

Member of the Imperial Earthquake Investigation Committee 
Tokyo, Japan 

Harold W. Fairbanks Mary Austin 

Berkeley, Cal. , J a »» Author of "Land of Little Rain" 

M "The Flock," Etc. 



1907 

M.ROB ERTSON 

San Francisco 






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DEC 18 I90f 

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COP YRIG HT BY 

A. M. ROBERTSON 




PRESS OF 

Bruce Brough 

SAN FRANCISCO 



Prefatory Note 



AFTER the Great Earthquake of 1906, a number of 
accounts of the matters of geology and engineering 
involved, appeared in the current magazines. One of 
these, published by the editor of the present volume, appeared 
in the Popular Science Monthly. The present publisher, 
Mr. Robertson, asked the privilege of reprinting this article, 
with such others of similar nature, as might be available for 
the purpose of a volume treating of the scientific aspects of the 
Great Earthquake. 

The essays thus chosen constitute the present volume. Those 
of Professor Branner and Mrs. Austin are reprinted from 
Out West, by the courtesy of the editors, Charles F. Lummis 
and Charles Amadon Moody; the essay of Mr. Gilbert and 
that of the present writer are reprinted from the Popular 
Science Monthly by the courtesy of the editor, Professor J. 
McKean Cattell ; the essay of Mr. Taber is reprinted from 
The Journal of Geology by the courtesy of Professor Thomas 
Chrowder Chamberlain; that of Professor Omori, from the 
Bulletin of the Imperial Earthquake Investigation Committee 
of Japan, by the courtesy of this Commission; that of Mr. 
Fairbanks, from the Bulletin of the California Physical 
Geography Club, by the courtesy of the Club. Professor 
Derleth's essay was written expressly for the purpose of this 
volume, appearing here for the first time. It is believed that 
the series of articles give a clear, comprehensive, and accurate 
view of the Great Earthquake and its associated phenomena. 

David Starr Jordan. 
Stanford University, 
April 18, 1907. 



[v 



Contents 

PAGE 

The Earthquake Rift of April, 1906. By David Starr 

Jordan, President Stanford University . . . 1-62 

Geology and the Earthquake. By John Casper Bran- 
ner, Vice-President and Professor of Geology, 
Stanford University 63-78 

The Destructive Extent of the California Earthquake 
of 1906; Its 'Effect Upon Structures and Struc- 
tural Materials, within the Earthquake Belt. By 
Charles Derleth, Jr., Associate Professor of 
Structural Engineering, University of California 79-212 

The Investigation of the California Earthquake of 
1906. By Grove Karl Gilbert, of the U. S. Geo- 
logical Survey 213-256 

Local Effects of the California Earthquake of 1906. 

By Stephen Taber, Stanford University . . 257-280 

Preliminary Note on the Cause of the California 
Earthquake of 1906. By F. Omori, Sc. D., Mem- 
ber of the Imperial Earthquake Investigation 
Committee, Tokyo, Japan 281-318 

The Great Earthquake Rift of California. By 

Harold W. Fairbanks, Ph.D 3 I 9~338 

The Temblor: A Personal Narration. By Mary 
Austin, Author of "Little Rain," "The Flock," 
etc 339-36i 



vn 



List of the Illustrations 

PAGE 

The Town Columns Frontispiece 

Relief Map of California 3 

Earthquake Rift, As It Comes up from the Sea at Point Arena, 

Mendocino County 6 

Fissure and Landslip, San Jacinto Valley, 1897 8 

Alder Creek Bridge, Mendocino County. The Earthquake Rift Is 

near the Middle of the Picture 10 

Tomales, Marin County. The North Shore Railroad and the 

Earthquake Rift 11 

Point Arena. Picket Fence Was in One Continuous Line. Photo- 
graph Shows Short Section Put in to Fill up Offset by Land on 

the West Side 12 

Landslip at Sobrante 13-14 

Marshall Hotel, Thrown into Tomales Bay 15 

Earthquake Crack in Country Road from Olema to Point Reyes . 16 
Earthquake Rift, Freeman's Ranch, near Tomales Bay . . . 17-18 
Train Overturned by Earthquake, Point Reyes Station, Marin 

County, Cal 21 

Earthquake Rift, Olema . 22 

Skinner's Ranch, Olema 23 

Earthquake Rift, Morrill's Ranch, Skylands, Santa Cruz County . 26 

Earthquake Rift, Morrill's Orchard, Santa Cruz County .... 28 

Inverness Road, near Olema, Marin County 29 

Wreck of Loma Prieta Sawmill, Hinckley's Gulch, Santa Cruz 

Count}- 30 

Site of Loma Prieta Sawmill, Covered to the Depth of 125 Feet . 31 

Old Bogoslof or Castle Island 36 

Fire Island, One of the Old Bogoslof Islands 37-39 

New Bogoslof, or Fire Island (1883) 41 

The New Bogoslof Island 43 

Bogoslof of May, 1906. From New Bogoslof, or Fire Island . . 44 

The Three Bogoslofs, May, 1906 45 

Slump in Soft Ground, Milpitas 66 

Rift Crossing Road, near Skylands, Santa Cruz County, Showing 

Relative Sinking of West or Uphill Side of Rift 67 

Rift Across Road near Azul Springs, Santa Clara County ... 69 

House Over Rift near Saratoga Springs, California 70 

Redwood Snapped Off by Earthquake near Fort Ross, Cal. ... 72 
The Fault Passes Under a Live Oak and Uproots It, Woodside, 

Cal. 74 

Rift on Shafter's Ranch, Olema, Cal 75 

*Fig. 1 — Relief Map of San Francisco Peninsula. By Professor 
Andrew C. Lawsox : Consult Fifteenth Annual Report, U. S. 

Geological Survey, Page 405 89 

Fig. 2 — Map of California, Showing Position of Fault Line, Earth- 
quake of 1906. Reprinted from "Engineering News," June 28, 

1906 93 

* The figures are numbered separately for the separate articles. 

[ix] 



List of the Illustrations 



PAGE 

Fig. 3 — Redwood Tree, Situated on the Fault Line, near Fort Ross, 

Sonoma County, California 103 

Fig. A — Pine Tree Standing on the Line of Fault near Fort Ross, 
Sonoma County; the Ruptured Surface Shows the Character- 
istic Appearance of Newly Plowed Ground 105 

Fig. 5 — Fence near Fort Ross, Sonoma County, California, Offset 
Nine Feet at the Line of Fault 109 

Fig. 6 — Fence near the North End of San Andreas Reservoir, San 

Francisco Peninsula, Offset Seven Feet at the Line of Fault . 112 

Fig. 7 — Santa Rosa Flour Mill. A Typical Brick Structure with 
Wooden Interior, Three Stories in Height; the Major Portion 
Completely Collapsed 115 

Fig. 8 — Carnegie Library, Santa Rosa. A Typical Brick Building 
with Wooden Interior Framing; the Outer Walls Faced with 
Cut Stone. Buildings of This Type of Construction Invariably 
Were Shattered near the Roof Lines. The Picture Is Repre- 
sentative of the Behavior of Stone-faced Buildings with In- 
adequate Wood Framing 115 

Fig. 9 — A Scene in Santa Rosa Photographed Shortly After the 
Earthquake and Fire. The View Shows the Corner of Fourth 
and Mendocino Streets. The Ruins of the Court-House Face 
Mendocino Street. On the Left in the Picture Is Seen the 
Collapsed Keegan-Brush Building, a Two-Story Brick and 
Stone Structure, Devoted to General Store Purposes. This 
Building Did Not Burn, and Ninety Per Cent of the Stock 
Was Saved. On the Right Side of Mendocino Street the Fire 
Destroyed Everything. In This Respect the Picture Is Instruc- 
tive in That It Shows the Difference in the Destruction by 
Earthquake and Fire 117 

Fig. 10 — The Collapsed Court-House Dome, Santa Rosa. The 
View Is Taken with the Camera on the Second-Story Roof; 
See Fig. 9. The Court-House Consisted of Three Stories of 
Brick, the Third Story Smaller in Plan Than the Other Two. 
The Third Story Supported the Wooden Dome 118 

Fig. 11 — Street Surface in Front of the Ferry Tower, Showing 

Undulations and Cracks in the Asphalt Pavement .... 123 

Fig. 12 — Rupture of Car Tracks and Pavement on East Street, 

Corner of Pacific Street 125 

Fig. 13 — Scene Corner of Howard and Seventeenth Streets Show- 
ing Rupture of Car Tracks, Sewer, Water and Gas Pipes . . 126 

Fig. 14 — Collapsed Frame Houses on Howard Street, between 17th 
and 18th Streets. The One on the Left Is Completely Razed. 
At This Place the Earth Movements Were Especially Severe, 
and Even Good Construction Would Have Suffered .... 127 

Fig. 15 — Frame House Wrecked in Santa Rosa; Due to Weak and 

Decayed Underpinning 129 

Fig. 16 — Collapsed Frame House in San Jose Showing the Effect 
of a Lack of Transverse Framing and an Absence of Continuity 
in the Vertical Sticks at the Floor Levels 129 



[x 



List of the Illustrations 



PAGE 

Fig. 17 — A San Jose High School. Ordinary Brick Construction 

with Wooden Interior 134 

Fig. 18 — St. Francis Church, San Francisco ; an Example of Ex- 
cellent Brickwork 135 

Fig. 19 — First Baptist Church, Oakland, California. The Danger- 
ous Tower Was Pulled Down Several Days after the Earth- 
quake ... 136 

Fig. 20 — Fire Ruins of a Power-House of the San Francisco Gas 
and Electric Company, Station C. The Chimney of This 
Structure Fell During the Earthquake Shock, Demolished a 
Part of the Equipment and Killed One Person 138 

Fig. 21 — The Mills Building, San Francisco ; Self-Supporting Brick 
Walls, Interior Framing of Steel, Floors and Partitions of 
Hollow Tile 139 

Fig. 22 — Fire Ruins of the Cowell Building, a Class B Structure, 

Showing the Great Destruction by Fire . . 140 

Fig. 23 — The Monadnock Building, Showing Heavy Diagonal 
Cracks in the Brick Curtain Walls along the Northeast Corner 
for the Full Height of the Structure 147 

Fig. 24 — Flood Building, Northwest Corner, Showing Heavy Earth- 
quake Cracking of the Sandstone Masonry Enveloping the 
Steel Corner Column 149 

Fig. 25 — St. Francis Hotel, Southeast Corner, Showing Heavy 

Earthquake Cracks in the First Story of the Sandstone Front 151 

Fig. 26 — Fairmont Hotel ; North Front, Showing Earthquake 

Cracks in the Terra-Cotta Veneer of the Second Story Walls 153 

Fig. 27 — General Postoffice, Southwest Corner, Showing Severe 

Distortion and Subsidence of the Sidewalk and Street Levels . 154 

Fig. 28 — Earthquake Cracks on Sandstone Piers of the Ferry Build- 
ing. These Piers Enclose Steel Columns with a Complete Air 
Space between the Steel Columns and the Stone Blocks. This 
Explains the Large Amount of Cracking and Shows That the 
Stone Piers Are Not Required for the Support of the Second 
Story 155 

Fig. 29 — The Ferry Tower Shortly after the Earthquake . . . 157 

Fig. 30 — Taken from the Report of the Committee on the Effect 
of the Earthquake on Water- Works Structures, American So- 
ciety of Civil Engineers ; Proceedings, Vol. XXXIII, March, 
1907 159 

Fig. 31 — Rupture of the 44-inch Crystal Springs Conduit on the 
San Bruno Marsh; Picture Taken May 2, 1906. The Wooden 
Supports Under the Pipe Are Temporary Forms Built after 
the Catastrophe. The Pipe Has Been Straightened Prepara- 
tory to Repairing the Transverse Riveted Joints 166 

Fig. 32 — Rupture on Crystal Springs Pipe Line, San Bruno Marsh . 167 

Fig. 33 — Crystal Springs Conduit between San Mateo and Millbrae. 
Temporary Cut-Off to Stop the Flow of Water toward San 
Francisco and Yet Maintain a Pressure and Supply for the City 
of San Mateo 167 



[xi] 



i s t of the Illustrations 



PAGE 

Fig. 34 — Rupture on Pilarcitos Pipe Line near North End of San 

Andreas Reservoir 170 

Fig. 35 — Collapsed Trestle at Frawley Gulch, Pilarcitos Pipe Line, 

Spring Valley Water Company 171 

•Fig. 36 — Telescoped Rupture, Pilarcitos Pipe Line, Spring Valley 

Water Company 172 

Fig. 37 — Diagonal Ruptures, Pilarcitos Pipe Line, Spring Valley 

Water Company 173 

Fig. 38 — Diagonal Rupture, Pilarcitos Pipe Line, Spring Valley 

Water Company 174 

Fig. 39 — Collapse by Compression at a Small Trestle, Pilarcitos 

Pipe Line, Spring Valley Water Company 175" 

Fig. 40 — Gas Main Explosion, Valencia Street, near Market Street, 

San Francisco 180 

Fig. 41 — Arcade, Inner Quadrangle, Stanford University . . . 181 

Fig. 42 — Rear View Memorial Arch, Stanford University, Showing 

Arch Ring Intact 182 

Fig. 43 — Fallen Masonry from. Top of Memorial Arch, Stanford 

University, Showing Mortar Strength 183 

Fig. 44 — View at Agnews Showing the Complete Collapse of the 

Main Tower of the Asylum 185 

Fig. 45 — Earthquake Destruction, Native Sons' Hall, San Jose . . 186 

Fig. 46 — A View on First Street, San Jose, Showing Lack of Fram- 
ing for First Floor. These Buildings Were Later Pushed Back 
into Place 187 

Fig. 47— Hall of Justice, San Jose, Completed in 1905 . . . .189 

Fig. 48 — Rear View, Hall of Records, San Jose, Showing How the 
Heavy Stone Outer Walls Cracked Away from the Interior 
Framing Due to Improper Anchoring of Walls to Floors and 
Roof 190 

Fig. 49 — Pajaro River Bridge, Southern Pacific Railroad; Tempo- 
rarily Strengthened by Timber Bents and False Work ; View 
Taken May 30, 1906 191 

Fig. 50 — West Abutment, Pajaro River Bridge, Southern Pacific 

Railroad 192 

Fig. 51 — First Intermediate Pier, West End, Pajaro River Bridge, 

Southern Pacific Railroad 193 

Fig. 52 — South Abutment, Salinas Highway Bridge 195 

Fig. 53 — West Wall, the Spreckels Sugar Mill, near Salinas, Show- 
ing Bulged Wall and Brickwork Thrown from the Steel 
Frame 197 

Fig. 54 — North Wall, the Spreckels Sugar Mill, near Salinas, Show- 
ing Ruptured Brick Curtain Walls and the Advantages of a 
Class A Steel Frame 197 

Fig. 55 — Ruptured Conveyor, the Spreckels Sugar Mill near Salinas, 

Showing Slipping of the Ground into the River 199 

*Fig. 1 — Map Showing the Position of the Fault Which Caused the 

California Earthquake 217 



[xii] 



List of the Illustrations 



PAGE 

Fig. 2 — Fault Topography between Tomales and Bolinas Bays ; 
Looking Northwest. The General Slope Toward the Left Has 
Been Interrupted by a Slight Uplift of the Part at the Left. 
The Pond Occupies a Hollow Thus Produced 221 

Fig. 3 — This Fence, Previously Continuous and Straight, Was 
Broken and Parted by the Earthquake Fault, the Offset Being 
8^4 Feet. The Line of Fault, Concealed by the Grass, Crosses 
the Ground from Left to Right, Touching Both the Dissevered 
Ends of the Fence 225 

Fig. 4 — Diagrams Illustrating the Dislocation Causing the Cali- 
fornia Earthquake. The L T pper Represents an Earth Block 100 
Feet Square and 25 Feet Thick, with Indication of the Position 
of the Fracture. The Lower Shows the Relation of Its Two 
Parts after Faulting 228 

Fig. 5 — A Faulted Road near the Head of Tomales Bay. The 
Nearer and More Distant Parts of the Road Were Originally 
in One Line — a Continuous, Straight Road. The Present Off- 
set is Twenty Feet 231 

Fig. 6 — Ordinary Appearance of the Earthquake Rift Where It 

Traverses Firm Turf 233 

Fig. 7 — A Zone of Earthquake Fracture Where It Crosses a Road 

Near Bolinas 234 

Fig. 8 — Cracks Caused by the Shaking of Marshy Ground. The 
Comparatively Firm Road Embankment Preserved the Cracks 
Better than the Bog 237 

Fig. 9 — Street Scene in San Francisco, Showing the Effect of the 
Earthquake on Filled Ground. The Distant Part of the Street 
Probably Retains Its Original Level and Position. Nearer by 
the Ground Has Settled Several Feet and Has Also Moved 
to the Left 239 

Fig. 10 — Road Crack Caused bv the Earthquake 243 

Fig. 11— Small Landslide on the Uphill Side of a Side-Hill Road . 247 

Fig. 12 — Water Tank Thrown from Its Pedestal by the Earth- 
quake 249 

Fig. 13 — School-House at Point Reyes Station, Near Inverness ; 
Shifted Horizontally Two and One-Half Feet by the Earth- 
quake. The Corner Here Shown Was Slipped from the 
Foundation and Rests Directly on the Ground 250 

Fig. 14 — Diagrammatic Plan of a Portion of the Earthquake Fault, 

Illustrating Changes in Geographic Position 251 

*Fig. 1 — Map of the Stevens Creek Fault 261 

Fig. 2 — Fracture Along Old Fault Line During the San Francisco 

Earthquake 263 

Fig. 3 — Road Crossing the Fault Line Two Miles Southeast of Por- 
tola. There Is a Vertical Uplift on the Northeast Side of the 
Fracture at This Place 264 

Fig. 4 — Showing a Fence That Crossed the Fault at an Oblique 
Angle. The Post Shown in the Photograph Was Split and 
Pulled Apart and the Wires Broken 265 

F xiii 1 



i s t of the Illustrations 



PAGE 

Fig. 5 — Showing a Fence That Was Broken and Offset Eight Feet 

Where It Crossed the Fracture 266 

Fig. 6 — Photograph of a Fence Crossing the Fault-Line at Right 
Angles. The Man is Holding an Eight-Foot Transit Rod and 
Stands in Line with Continuation of the Fence on the Far 
Side of the Fracture. The Fence Was Repaired Before the 
Photograph Was Taken 267 

Fig. 7 — Dam at Crystal Springs Lake, Showing Cracks Formed by 

the Displacement 269 

Fig. 8 — An Oak Tree Six Feet in Diameter Uprooted by the Earth- 
quake Three Hundred Yards from the Fault Line .... 271 

Fig. 9 — Photograph of Arches at Stanford University, Showing 
Keystones Lowered During the Earthquake. These Arches 
Were Nearly at Right Angles to the Fault-Line 277 

*Fig. 1 — San Francisco and Vicinity, Showing the Course of the 

Great Fault from Pt. Arena to Chittenden 287 

Fig. 2 — San Francisco and Vicinity, Showing the General Course 

of the Great Fault 291 

Fig. 3 — Directions of Motion at Different Places on or near the 
Great Fault 291 

Fig. 4— 293 

Fig. 5— 294 

Figs. 6 and 7— 295 

Fig. 8 — The Shaded Parts Indicate Cracks of the Ground . . . 297 

Fig. 9— 297 

Fig. 10— 299 

Fig. 11 — The Shearing Effects on a Pier at Inverness, on the West 
Coast of the Tomales Bay. The End Part of the Pier Was 
Displaced About 20 Feet Towards NNW 301 

Fig. 12 — One of the Fault Cracks Produced Among the Hills Above 
Fort Ross. The New Disturbances Appeared Along a De- 
pression Marked by a Series of Small Ponds (Shown at the 
Right-Hand Side of the Picture), Which Are Traces Left by 
a Former Earthquake 301 

Fig. 13 — Remarkable Compression and Shear Effects Along One 
of the Fault Cracks, Produced on Elevated Grounds near 
Pt. Arena. A Foot-Scale Placed in the Foreground Shows the 
Size of the Overlapping Earth Pieces, Whose Plan Is Given 
in Fig. 8 305 

Fig. 14 — Some of the Cracks of Plastered Walls in St. James Hotel, 
San Jose 305 

Fig. 15 — The Damaged Condition of the Newly Erected Library of 
the Stanford University. The Central Steel Dome Behaved as 
an Elastic Inverted Pendulum 309 

Fig. 16 — The Ruined Condition of a Steel-Framed Brick House in 
San Francisco, Which Was Dynamited and Then Burnt, Show- 
ing the Remarkable Effects of the Intense Heat 309 

T xiv 1 



s t of the Illustrations 



PAGE 

Fig. 17 — The Observatory on the Top of the Strawberry Hill, in 
the Golden Gate Park, San Francisco, Built of Reinforced 

Concrete. An Outside View of the Back Part 313 

Fig. 18 — One of the Cracks of the Basement Wall. The Steel 
Cable, One Inch in Diameter, Which Was Embedded in the 

Concrete, Was Broken 313 

Fig. 20— i 315 

Lake in a Sunken Area on the Rift in Cholame Valley .... 323 

Effect of Recent Earthquake in the Ridge above Mussel Rock . . 325 

Road Displaced 12 Feet on Line of Rift at Head of Tomales Bay . 327 

Alkali Sink on Line of the Rift North of Bakersfield 329 

San Francisco on the Night of April 18 342 

Looking Southeast from Telegraph Hill During Fire 343 

Looking South from Lafayette Square, 4 p. m., April 18 ... . 345 

Van Ness Avenue, 10:30 p. m., April 19 347 

Jefferson Square 347 

"Nob Hill" After the Fire, Showing the Huntington, Crocker, and 

Flood Residences. Fairmont Hotel in Background .... 351 

In the Apartment House District 353 

Tivoli Theatre 353 

Fairmont Hotel After the Fire 357 



[XV] 



The Earthquake Rift 
of April, 1906 

By 

David Starr Jordan 

President Stanford University 



I he Earthquake Rift of 
April, 1906 

THERE are two sets of disturbances which 
shake the crust of the earth and therefore 
go by the name of earthquakes. Eruptive 
earthquakes are explosions, usually of steam, about 
a volcano. Tectonic earthquakes are breaks in the 
overloaded or overstrained crust of the earth, and, 
for the most part, have nothing to do with the 
steam vents we call volcanoes. To the last class 
most earthquakes belong, certainly almost all that 
have been felt within the United States. 

Again, under the name of earthquake we include 
two very different sets of phenomena, the one the 
rock-rift or fault, which is the disturbance itself, 
the other the spreading or interfering waves set in 
motion by the parting, shearing and grinding of 
the sundered walls of rocks in the earthquake fault. 
It is the jarring waves extending in widening and 
interfering circles which do the mischief to man 
and his affairs. It is the rift of rock which sends 
these waves forth on their blind mission of confu- 
sion and destruction. 

In every tectonic earthquake there is somewhere 
a fault or rift of rock, with some sort of displace- 



the California Earthquake of i g o 6 

ment, permanent or temporary, of the relations of 
the two sides. In extreme cases, this break ex- 
tends for miles in a straight line, breaking the sur- 
face soil and passing downward to a depth which 
can be only guessed at, five or ten miles perhaps, 
probably as far down as the crust is rigid. There 
are undoubtedly destructive earthquakes in which 
the soil is not broken oyer the rift of rock, but as a 
rule, in violent disturbances, the crack comes to the 
surface, breaking through the overlying soil. In 
all severe earthquakes there are, moreover, breaks 
or fissures in the earth having no connection with 
the fault itself. These are slumps or landslides, 
and geologically they signify but little. They mean 
simply that loose soil has been shaken down. They 
do not go down into the underlying rock. From 
the true earthquake crack they may usually be 
known at once, because their course is determined 
by the topography. They are not straight. The 
true earthquake rift moves on in straight lines, 
broadly speaking, careless of topography. But 
topography is not careless of the earthquake rift. On 
either side of it, for perhaps hundreds of feet, the 
rocks are crushed to flinders by the impact and 
grinding of the opposed walls. An old fault is 
therefore marked by an excess of erosion. A valley 
or saddle marks its general course. Streams choose 
it for their basins, and when it crosses a mountain 



_ 




Relief Map of California. 



David Starr Jo r d a n 

the softened rock yields to form a saddle or other 
form of depression. For these reasons, an earth- 
quake fault is often marked in California by succes- 
sions of dairies and of reservoirs. The valleys thus 
formed are fertile and well watered. For the most 
part, in much-faulted regions, such as form the rim 
of the Pacific, each earthquake rift follows the line 
of an old fault, and the original break goes back to 
the mountain-making periods of Tertiary times. 
The California earthquake of 1906 follows the axis 
of a very ancient break, the Tortola-Tomales fault/ 
also called the 'San Andreas fault/ first studied, so 
far as I know, by Dr. John C. Branner in 1891. In 
this fault hundreds of thousands of earthquakes, 
large and small, have preceded the recent one. In 
it the aggregate displacement horizontally has 
been very great, and the aggregate vertical dis- 
placement produced by all its many earthquakes, 
as shown by the rock strata on either side of it, ex- 
ceeds half a mile. 

From the rift at times in the past, masses of mol- 
ten rock have flowed out. Of such origin is the 
cliff of basaltic columns near San Francisquito 
Creek, on the Stanford University campus. Much 
more recent flows of black lava occur to the south- 
west of Stanford University and numerous dikes of 
lava occur for the whole length of the Santa Clara 

[5] 



*f h e Calif 



o r nz 



Earthquake of igo6 



Valley; these have not flowed from volcanoes but 
in times long past have escaped from rifts in the 
rock-producing earthquakes. 




ffi**f:pf*tofi 



Earthquake Rift, As It Comes up from the Sea at Point Arena, Mendocino County. 

An overflow of lava of this kind seems to be the 
origin of the picturesque 'Marysville Buttes' in 
Sutter County, and of Anacapa Island in the Santa 
Barbara channel. 

It is the purpose of this article to trace the earth- 
quake rift of April 18, 1906, across the map of Cali- 

[6] 



David Starr Jo r d a n 

fornia. The. accompanying photograph of a relief 
map by Dr. Noah Fields Drake will show the topog- 
raphy of the state. In California there are multi- 
tudes of valleys of various kinds. Those formed by 
water and ice surface erosion are variously curved 
and ramified. Such are the mountain canons of the 
west flanks of the Sierras. Those valleys formed 
or marked by earthquake cracks have almost in- 
variably straight axes. These extend in general 
toward the north-northwest, more or less distinctly 
parallel with each other, and often intersected by 
cross-faults. 

Examples of faulted valleys are the great valley 
of the Sacramento and San Joaquin, the Santa 
Clara Valley, San Francisco Bay, with the Valley 
of Santa Rosa, Eel River Valley, the Santa Catalina 
Channel, Owens River, the San Jacinto Valley and 
many others. A cross-fault extends from Monte- 
rey Bay up the valley of the Pajaro River. In some 
of these faults earthquakes have taken place in 
historic times, in others no break has been noted 
save that recorded in the rocks. Dr. Branner has 
compared a fault to a break in a bone. It represents 
a weak place which will give in a time of strain. 
On the other hand, if not freshly broken, it will 
tend with time to heal. A broken bone will be 
naturally renewed. A faulted rock bed will be 

[7] 



*? h e California Earthquake of i g o 6 



cemented in the course of ages of pressure and of 
cementation. Some of these rifts have been 
cemented and closed by their own lava-flows. This 
seems to have occurred in the case of the two ridges 
which bound the valley of Napa. 




Fissure and Landslip, San Jacinto Valley, 1897. 

The most interesting of these breaks in Califor- 
nia is that recorded as the Portola-Tomales fault. 
Its course can be plainly traced on the relief map. 
It enters the shore from the sea near the mouth of 
Alder Creek, to the north of the low headland called 
Point Arena, in Mendocino County on the north, 
and runs to Chittenden, on the Pajaro River, in 

[8] 



David Starr Jordan 

Monterey County, on the south. The line is al- 
most perfectly straight, and its course and direc- 
tion can be determined by placing a ruler on the 
map, using the line of Tomales Bay as an axis. 
This long, narrow, straight inlet is a resultant of 
past earthquakes, probably beginning in Tertiary 
times. It is bounded on the west by mountains 
which have their origin in some ancient upward 
thrust of the walls on the west side of the ancient 
fault. From Chittenden the same fault extends to 
the southward along the axis of the Gavilan Moun- 
tains for perhaps 300 miles more, quite straight, as 
far as Monte Pinos in Ventura County, past Priest 
Valley, Cholame and the Carisa desert. From 
Monte Pinos, it is said to curve to the eastward past 
San Bernardino and San Jacinto to near Yuma, 
but as to this eastward extension the present writer 
has no exact knowledge. 

On the eighteenth of April the trouble began in 
the sea. Just where, we may find out later. We 
know that the center is in the sea because where 
the rift enters the land the motion was more violent 
and the effects of the shock greater than at any 
other point along its extent. As the opened rift 
can be traced for 192 miles across the land to the 
southward from Point Arena, it is safe to say that 
it goes as far to the northward under the sea. The 



C F h e California Earthquake of i g o 6 

steamer Argo crossing it the moment of the earth- 
quake, off Mendocino, ninety miles to the north- 
ward of Point Arena, bears witness to this fact. 
The captain thought that he had struck a raft of 




Alder Creek Bridge, Mendocino County. The Earthquake Rift Is near the Middle 
of the Picture. 

logs, so fierce and hard were the shocks of the 
waves in the water. The movements were short, 
quick and violent, not forming a tidal wave, but a 
strange choppy sea. For the time being all rollers 
and surf were broken up. Off the bold headland of 
Cape Mendocino is a deep sub-marine valley, to the 

[10] 



D 



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west of which is a high mountain which does not 
rise to the surface of the ocean. In the channel 
between the cape and the submerged mountain the 
earthquake rift may be supposed to run. In this 
channel numerous earthquake shocks have been 




Tomales, Marin County. 
Earthquake Rift. 



The North Shore Railroad and the 



recorded by different passing vessels. If not itself 
a center of disturbance, it records the line along 
which great disturbances have frequently passed. 
The rift struck the land at the mouth of Alder 
Creek, above Point Arena. It crept over the hill 
as a deep furrow in the black, sticky adobe, veering 
a little to left or right according to the resistance 
of the soil, but always keeping in a straight line 

[ii] 



tf h e California Earthquake of i g o 6 

in its general direction. It may be imagined as a 
sort of devouring dragon, leaving its trail on the 
hills and destroying the works of man wherever 
it passes. It is hard in following its course, not to 
think of it as endowed with a sort of wicked life. 




Point Arena. Picket Fence Was in One Continuous Line. Pho- 
tograph Shozvs Short Section, Put in to Fill up Offset by 
Land on the West Side. 



Its movement is properly from north to south, but 
the opening of the great fault seems to have been 
really instantaneous. It took place at 5:13 a. m. 
and the waves lasted forty-seven seconds. It may 
be noted in passing that the complication of the 
waves at any one point was mainly due to the great 
length of the rift. A point immediately near the 
crack felt mainly the first great shock, its wave and 

[12] 



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the return wave. A point farther away felt the 
wave and its return jolt, followed at once by waves 
from farther to the north and farther to the south, 
these waves becoming more and more opposed to 




Landslip at Sobrante. 



one another. The waves would then augment, neu- 
tralize, override and otherwise modify one another, 
the final result being the violent twisting motion, 
the most remarkable trait of the latter portion of 
the earthquake in question. 

Coming over the first ridge, from the sea, the rift 
passed under the long bridge over Alder Creek. 

[13] 



tf h e California Earthquake of i g o 6 

The land on the west side of the bridge was jerked 
sixteen feet to the north; or that on the east six- 
teen feet to the south — only a careful re-survey of 
the region can tell us which. For this information 




Landslip at Sobrante. 



we must depend on the work of the U. S. Coast and 
Geodetic Survey. Or it may be that both sides 
went to the northward, but the west side pulled 
away, distancing the other by sixteen feet. In any 
case, the bridge was torn to splinters, and the crack 
went on, always the west side some sixteen and 
a half feet to the northward, though the sticky soil 
tends to lag back, and not every place shows the 

[i4] 



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Marshall Hotel, Thrown into Tomales Bay. 



maximum of shearing or horizontal displacement. 
Passing under a barn, the rift tore it to splinters. 

The spreading wave 
displaced or destroyed 
most of the houses 
in the villages of 
Manchester and Point 
Arena, wrecking the 
magnificent lighthouse 
of solid masonry on 
the Point itself. In low 
ground the rift form- 
ed successions of little 
ponds. On hillsides 
the lower side of the crack fell away like a drivel- 
ling lower lip, leaving an open chasm, ten to twenty 
feet in apparent depth. On level hard ground the 
soil like the rock below closed with a snap a little 
tighter than it was before. Line fences were broken 
and sheered from sixteen to twenty feet. Lines of 
trees met with similar readjustments. In Mendo- 
cino County the horizontal displacement is about 
sixteen feet. In Marin County, wherever it is ex- 
actly measured, it is sixteen feet and seven inches. 
Southward it becomes less. In San Mateo County 
it is six to eight feet, and at the Pajaro Bridge at 
Chittenden, near which point the open fault 
ceases, the western pier was moved northward 



*5 



7* h e California Earthquake of i g o 6 

about eighteen inches. This shifting of position, 
evident along the line of the crack, seems to have 
included the whole region, mountains and valleys 
through which the crack passes. Either the region 
to the westward with the Santa Cruz Mountains 
and the mountains called Sobrante de la Punta de 
los Reyes have been stretched out toward the north- 
ward or else the re- 
gion on the east side, 
including most of Cali- 
fornia, has been cor- 
respondingly humped 
up. It is impossible at 
present to say which 
is the fact, perhaps 
both. The vertical dis- 
placement is small. To 
the north of San Fran- 
cisco the west side has 
been raised two or 
three feet. To the 
southward the slight 
relative change in ele- 
vation — two or three feet — is in favor of the east side. 
The rift left the pastures of Point Arena, passing 
up Gualala River, always in a straight line, making 
havoc among the redwood trees and still greater 
havoc in the town of Fort Bragg which was in part 




Earthquake Crack in Country Road from 
Olema to Point Reyes. 



16] 



David 



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shaken down, and afterwards burned. From Men- 
docino County it passes into the sea, where it runs 
close along the coast of Sonoma County past Fort 
Ross, throwing down everything movable in this 




Earthquake Rift, Freeman's Ranch, near Tomales Bay. 



and other towns. It then crosses Bodega Head 
and again falls into the sea, where it passes up the 
axis of Tomales Bay. At the head of the bay its 
course through the tules or bulrushes looks like a 
swath through a grain field. Through this region 
(Marin County) the shock was very violent, and 
numerous cracks parallel with the main crack in 

[17] 



tf h e California Earthquake of i g o 6 



the bay extended along the shores. In the town 
of Tomales, much and varied mischief was done. 
The parallel cracks toyed with miles of the North 
Shore Railroad between Tomales and Point Reyes. 




Earthquake Rift, Freeman's Ranch. 

At Marshall the humble hotel was thrown bodily 
— and upright — into the bay, the boarders un- 
harmed; and at aristocratic Inverness, on Tomales 
Bay, three summer cottages suffered the same fate. 
A fisherman in the bay reports that the waters of 
Tomales Bay receded, leaving his boat in the mud. 

[18] 



David Starr Jo r d a n 

Afterwards they came back in a 'great wave, which 
looked a hundred feet high, but which was 
probably not more than ten.' 

At Point Reyes Station at the head of Tomales 
Bay the 5:15 train for San Francisco was just 
ready. The conductor had just swung himself on 
when the train gave a great lurch to the east, fol- 
lowed by another to the west, which threw the 
whole train on its side. The astonished conductor 
dropped off as it went over, and at sight of the fall- 
ing chimneys and breaking windows of the station, 
he understood that it was the temblor. The fire- 
man turned to jump from the engine to the west 
when the return shock came. He then leaped to 
the east and borrowing a kodak he took the picture 
of the train here presented. 

Paper Mill Creek runs past the same village, a 
considerable stream, noteworthy lately from the 
experiments in stocking it with king salmon. The 
two banks of the stream were forced toward each 
other so that the length of the bridge was short- 
ened by about six feet and the bridge was cor- 
respondingly humped at its north end, an arch 
about six feet high being forced up. 

From Point Reyes Station (at the base of the 
large peninsula called Point Reyes) the earthquake 
rift passed along the Inverness Road to Olema, 
where all the houses not standing on rock founda- 

[19] 



*f h e California Earthquake of i g o 6 

tion were thrown from three to six feet to the west- 
ward, toward the crack itself. 

Skinner's Ranch is a large dairy near Olema. The 
house stands near the road, a dairy house some 
thirty feet to the south of it, and a large barn with 
cowyard just behind that. A row of large cypress 
trees stood just before the house on the roadside, 
between them and the house a little rose garden, 
to the south of these, opposite and partly behind 
the dairy, a group or row of large eucalyptus trees. 
The earthquake rift passed directly in front of 
the house, between the buildings and the road. All 
that stood to the westward of the crack was vio- 
lently jerked to the north a distance of sixteen feet 
seven inches, or it may be that the east side moved 
an equal distance to the south. If Mr. Skinner had 
chanced to look at the right instant he would have 
seen the whole row of cypress trees file past his 
window to take their station in front of the dairy, 
taking the rose garden with them. A few rasp- 
berry bushes came from farther north to take, 
partly, the place of the roses. The eucalyptus trees 
in front of the dairy moved on to a position oppo- 
site the barn, and one detached from the others and 
to the westward of the crack was left near the head 
of the line instead of at its foot. The crack passes 
obliquely under the barn, entering it at the north- 
west corner and leaving it at the middle of its pos- 

[20] 



David 



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terior or southwest side. The barn remained in- 
tact, thanks to its weak foundation, for the east 
side pulled loose from the ground, and the barn 
went northward with the west side. Sixteen and 




Train Overturned by Earthquake, Point Reyes Station, Marin County, Cal. 

one half feet of its former foundation at the south- 
eastern corner is exposed. A driveway under the 
barn is divided in the middle. You pass in on the 
east side, the western half is sixteen and one half 
feet to the north of the entrance and completely 
blocked in the middle. Under each of the east win- 
dows of the barn stood a pile of manure. Each pile 

[21] 



T* h e California Earthquake of i g o 6 

is intact, sixteen and one half feet south of the win- 
dow to which it belongs. The people at the ranch 
were milking at the time of the shock. Each man 
and cow was thrown to the ground and it took two 




Earthquake Rift, Olema. 

hours to get the frightened cattle back into the 
'corral.' The stone steps to the basement of the 
dairy, on the east side of the crack, now stand six- 
teen feet seven inches to the southward of the door 
to which they led. About Skinner's, line fences and 
water pipes crossing the fault were broken, a 
break of sixteen and one half feet being left 

[22] 



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in each case, the west side of the fault 

in all cases more or less overriding the other. 

In the matter of line fences interesting legal 

problems are raised. Were the farms on the west 







■M jlffi/J^ 


v4, # 


3&JL. 








3T3WHI 


****. 


■ f 




v*". ' '■*$ 


■^w 








%: 






»;^ ' ;: 



Skinner's Ranch, Olema. 

stretched sixteen and one half feet or those on the 
east side crowded together to the same amount? 
If either, who stands the loss and what store can be 
set on ancient landmarks ? The observations of Dr. 
Grove K. Gilbert, verified by other geologists, leave 
little doubt that both sides of the rift moved, the 
west side to the northward, the east side to the 

[23] 



T he California Earthquake of i g o 6 

southward. How far from the rift this motion ex- 
tends to the east and to the west, is yet to be shown, 
manifestly it is a local, not a continental, change of 
position. 

Next to the Skinner Ranch is the Shafter Ranch. 
Here the houses and barns are on the east side of 
the crack, but the transposition of roads, trees and 
fences was the same in kind. The rift passed 
through the corral, and one of the astonished cows 
dropped into it, soon falling deeply till only rump 
and tail were visible. The hysterical. dogs barked 
at her, the water came into the rift, and the dairy- 
men, doubtless with a sense of the impotence to 
struggle against fate, buried her in the grave from 
which they could not rescue her. 

Crossing the valley the rift split a small hill, 
throwing down four large spruce trees, all of which 
fell at right angles to the crack. A very large oak 
tree standing on level ground was shoved violently, 
still standing, sixteen and one half feet to the south- 
ward into the base of the riven hill, or perhaps the 
western half of the hill was shoved violently about 
the tree. 

On through the valley of Olema went the rift, 
past more dairies, but leaving their buildings alto- 
gether to the east. Crossing the road above Boli- 
nas, the two sides of the highway are rudely sepa- 
rated. Reaching Bolinas Bay, the rift is visible in 

[24] 



David Starr Jordan 

the mud at low tide, and careful observers report 
the sea-bottom to the westward, along Duxbury 
Reef, to be raised two or three feet. The gatherers 
of abalone shells venture out into regions of sea- 
bottom formerly inaccessible at the lowest tides. 
On the east side of Bolinas Bay the clams are hope- 
lessly buried. At Bolinas the pretty Flagstaff Inn 
was thrown bodily into the sea and completely 
wrecked. The crack again enters the sea, passing 
across the entrance to the Golden Gate five or six 
miles west of the center of San Francisco, and giving 
to that breezy and joyous town a jolt which will live 
in history, and causing through the subsequent fire 
a greater destruction of the results of human effort 
than was ever known before in the records of the 
world. The rift reached the shore again at Mussel 
Rock to the southwest of San Francisco. Here the 
cliff was hurled down, a gradual incline was made 
a steep one and four thousand feet of newly graded 
railroad was thrown into the sea. It passed up the 
narrow valley of San Andreas, not harming the res- 
ervoir on account of the splendidly built dams of re- 
enforced concrete, but wrecking all the water mains 
entering San Francisco from the great reservoirs, 
Crystal Springs, San Andreas and Pilarcitos. The 
dam of the Crystal Springs reservoir, across the 
fault line, was also so well built that the visible 
crack passed around it along the bank by its side, 

[25] 



T h e California Earthquake of i g o 6 

returning- afterwards to its former direction. The 
bleak and boulder-strewn saddle called Canada del 
Raymundo, scarred by previous earthquakes, was 
then passed, and beyond it the narrow, fertile val- 




harthquake Rift, Morrill's Ranch, Skylands, Santa Cruz County. 



ley of Portola, named for its discoverer, Gaspar de 
Portola, the first governor of California, the dis- 
coverer of San Francisco Bay. The crack runs along 
the base of the Sierra Morena, four to five miles 
west of Stanford University, at the corner of its 
generous campus, to the head of Portola reservoir; 

\26] 



David Starr Jo 



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then ascends in a canon to a saddle on the summit, 
connecting two parallel ranges, Monte Bello to the 
east and Castle Rock to the west. Down from the 
saddle between these runs Stevens Creek (Arroyo 
de San Jose de Cupertino) and down this creek 
went the earthquake crack, tearing up the road be- 
hind it, and throwing down landslides from every 
steep slope. Stevens Creek is made up from the 
union of two streams which meet from opposite 
directions. The crack descends the one and re- 
mounts impartially in the valley of the other. Both 
streams follow old earthquake tracks. Over an- 
other saddle the crack goes to Saratoga Creek. 
Across it and over another saddle it follows Camp- 
bell Creek, draining its reservoir. Thence It crosses 
obliquely the valley of Los Gatos Creek, over the 
hills of which Bret Harte wrote — 

The ridges round Los Gatos Creek 
Arched their spines in a feline fashion, 

in the earthquake of 1818. Into this creek, from the 
Feely ranch, some ten acres of land was thrown in 
a great landslide. At the head of the creek is the 
long tunnel which cuts under the saddle, from 
Wright's to Laurel. This tunnel has been the 
source of endless trouble since it was made, and for 
the reason that the rock in the mountain through 
which it passes is made up of minute chips of stone. 
No wonder, for the earthquake crack follows the 

[27] 



1? h e California Earthquake of i g o 6 



mountain ridge, which is here narrow and low. It 
cuts tunnel and railroad track at right angles, and 
every earthquake disturbance is sure to make mat- 
ters worse. Already forty feet of crushed rock has 
fallen from above what was the roof of the tunnel. 
On the hill above the tunnel is Morrill's fruit ranch. 




Earthquake Rift, Morrill's Orchard, Santa Cruz County. 

The earthquake ripped its way through the or- 
chard, shifting the rows of trees six to eight feet 
and treating roads and fences in the same reckless 
fashion. The large hospitable Morrill farmhouse 
stood partly over the track and was split in two and 
utterly ruined. Farther on at Skylands, on the ridge 
of the mountains, Fern Gulch was filled with wreck- 
age; redwood trees four and five feet through, two 
or three hundred years old, were snapped off like 

[28] 



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dan 



whip-lashes. The rift crossed Hinckley's Gulch at 
right angles. This is a narrow gorge about a hun- 
dred feet deep, in which stood the large Loma 
Prieta sawmill. The gorge was filled by landslips 
thrown from both 
sides. The mill was 
completely buried,with 
nine mill hands, and a 
redwood tree over a 
hundred feet high was 
set erect and unhurt 
over the place where 
the mill stood. The 
bodies of six men were 
recovered. One of 
these, the foreman, 
was found erect, 
smothered in mud, but 
standing with extend- 
ed arms and limbs in 

. , r . Inverness Road, near Olema, Marin 

the act of running county. 

from the mill. With him, equally erect and in the 
act of running was the body of a Siberian mastiff. 
Their position marked the meeting point of the two 
walls of the canon. The crack went on across the 
hills, always in the same direction, southeast by 
south, till it came to the Chittenden Ranch in the 
Pajaro Valley. Here it tore off the hillside, 




[29 



tf h e California Earthquake of i g o 6 



destroying the highway at its base; then descended 
to the Pajaro River, shifting a pier of its railroad 
bridge about eighteen inches to the northwest. 
Here it met the Pajaro cross-fault. But here the 
straight line from Point Arena came to an end. 




Wreck of Loma Prieta Sawmill, Hinckley's Gulch, Santa Cruz 
County. 

A series of short breaks creeps off to the southeast, 
ending two miles southwest of San Juan, the last 
act being the final, almost complete wreck of the 
beautiful and venerable Mission of San Juan 
Bautista. 

That the oblique crack from Chittenden, famous 
as an 'earthquake ranch' of earlier times, to San 
Juan, is part of the original rift, is not clear. It 
may be that this is part of the Pajaro cross-fault. 

[30] 



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The original Portola-Tomales fault, if continued 
in a straight line from Chittenden, would pass 
along the flanks or the foot of the Gavilan moun- 
tains to Priest Valley, fifty miles to the south- 
southeast. Beyond Priest Valley is a well-marked 




Site of Loma Prieta Sawmill, Covered to the Depth of 123 Feet. 

earthquake crack, which opened in the earthquake 
of 1868, and in earlier times. This extends through 
desert land in the same direction, its course being 
the axis of the Cholame Valley and the uninhabited 
desert sink known as Carisa Plain. This old rift 
extends at least one hundred and forty miles be- 
yond Chittenden to Monte Pinos in the north edge 
of Ventura County. This whole fault from Point 
Arena to Monte Pinos is clearly a single break, but 

[31] 



The California Earthquake of i g o 6 

only 192 miles of a possible 330 were opened in 
the earthquake of 1906. 

But while the surface break seemed to end at 
Chittenden, it seems probable that the rift in the 
rocks below extended much farther. At Priest 
Valley, fifty miles along this line, the shock was 
violent, while at localities ten miles or more to the 
east and west of the line, as at Lone Oak* or the 
Pinnacles, it was very little felt. In Priest Valley 
chimneys and shelving were thrown down, build- 
ings badly shaken and the contents of a country 
store impartially scattered over the floor, the shock 
being apparently about as severe as in San Fran- 
cisco. 

With the opening of the great rift it is conceiv- 
able that faults in the neighborhood should also be 
affected. There is some evidence (most of which 
the writer has not examined) of the opening of a 
parallel fault behind Cape Mendocino. This seems 
to have passed across the base of the cape, cutting 
across the smaller headland called Point Delgada, 
losing itself in the Sonoma Valley to the southwest 
of Santa Rosa. There are distinct traces of great 
disturbance across Burbank's famous orchard at 
Sebastopol, but it is not clear that in any of these 
the underlying rock is really broken. Here on a 



* Spelled Lonoak by the economical and iconoclastic Postoffice 
department. 

[32] 



David Starr Jordan 

slope lines of fruit trees were shifted, a well was 
moved bodily three or four feet, and a crack about 
one fourth mile long extended across a neighbor- 
ing field, its direction parallel with that of the To- 
males rift. Other similar cracks open at intervals 
on the road toward Point Delgada. At Sobrante, 
in Contra Costa County, east of San Francisco Bay 
there are large slumps or cracks in the earth. The 
extreme violence of the shock in Santa Rosa per- 
haps indicates its nearness to this second rift, as 
the Tomales rift caused little damage in other 
towns equally far away. In some maps of the 
earthquake rift it is marked as swinging to the 
eastward in a curve across Point Delgada to the 
eastward of Cape Mendocino, between that Cape 
and Humboldt Bay. It seems to the present writer 
far more probable that the Point Delgada fault is 
a separate rift, parallel with the main rift, and 
similar to it, except that it is a little less violent. 
There is some evidence that a fault line at the foot 
of San Francisco Bay opened for a short distance 
to the southward of Milpitas. But the soft soil 
in that region was filled with slumps and cracks 
due to the shaking down of loose deposits, and one 
could not be sure that the actual fault in the rocks 
was really disturbed. The same remark applies to 
the breaks at San Bruno about ten miles south of 
San Francisco in marsh deposits. It is readily 

[33] 



tf h e California Earthquake of i g o 6 

conceivable that a great disturbance like the one 
in the main fault might be accompanied by similar 
breaks in parallel or associated faults. Or it may 
be that all these breaks like those in the streets of 
San Francisco are due wholly to the slump of loose 
or wet ground. 

The studies and experiments made by Professor 
Branner on the effect of shocks on dry and wet 
earth leave no doubt that earthquakes are much 
more severe when the soil is saturated with water. 
The earthquake of April 18 came at the end of the 
rainy season, and after a period of great wetness. 
The soil of the lower grounds along the Bay and in 
the neighboring valleys rested on gravel saturated 
with water, and this wet ground was thrown into 
visible waves by the shocks of the earthquake. On 
the hills and on rock foundation the shock was in- 
tense and sharp, but without these destructive sur- 
face undulations. In midsummer all the ground 
would be relatively hard and the injury to buildings 
would be very much less, considering shocks of like 
degree of original intensity. 

The chief center of disturbance in the earth- 
quake of 1906 would seem to be in the sea. The 
evidence for this lies in the fact that at the point 
where the fault enters the land near Point Arena 
the displacement is greater than anywhere else. 
As the land fault is traceable for nearly two hun- 

[34] 



David Starr Jo r d a n 

dred miles to the southward, it is reasonable to 
suppose that the sea-bottom is broken for at least 
an equal distance to the northward. The point of 
earthquake disturbance off Cape Mendocino has 
been frequently noticed in the past, and this is in 
a right line with the rest of the fault. It is possible 
that the center of trouble is located in the valley 
between Cape Mendocino and the off-lying sub- 
marine mountain. 

There is also another possibility, very remote 
perhaps, but still worth considering, that is, the 
connection between this rift and the disturbances 
about the islands of St. John Bogoslof, in Bering 
Sea. 

In the southern portion of Bering Sea, about 
thirty-seven nautical miles northwest from the 
island of Unalaska, lies a group of small volcanic 
islets known as Bogoslof in Russian, Joanna 
Bogoslova, St. John, the Theologian. There are 
now three of these, all of which have risen from the 
sea, hot and steaming, within historic times. An 
especial interest attaches to them just now from the 
fact that the third and largest of the group ap- 
peared at about the time of the great earthquake 
of April 18, 1906. So far as known its rise must 
have taken place in March, 1906. 

The possibility of a connection between the dis- 
turbances at Bogoslof and those which caused the 

[35] 



T 'he California Earthquake of i g o 6 

California earthquake is heightened by the fact that 
the great earthquake rift, which extends through 
the Coast Range of California for a distance of 200 
miles, follows a direction, which, if produced north- 




Old Bogoslof or Castle Island. 



ward to Bering Sea, would pass near the islands 
of Bogoslof. Again this earthquake rift was largest, 
and its effects more violent, where it entered the 
sea in Mendocino County than at any other point 
throughout its course. 

In opposition to this view may be placed the im- 
probability that an earthquake rift or fault would 
extend so far as from the center of California to 

[36] 



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Bering Sea, a distance of more than 2,000 miles, and 
through such great depths of water as intervene 
between Point Arena and Bogoslof. It is also 
stated that the evidence of the seismograph, so far 




Fire Island, One of the Old Bogoslof Islands. 

as understood, favors the idea that the great earth- 
quake was confined to California. 

It is evident also that the rise of the third Bogos- 
lof was attended by little if any disturbance in the 
immediate vicinity. The advent of each of the 
other two islands was marked by earthquake 
shocks, the fall of volcanic ashes and displays of 

[37] 



tf h e California Earthquake of i g o 6 

B = 

fire, observed and felt by the people of Illiuliuk on 
Unalaska Island. The people of this village in 1906 
were unaware of the presence of the new island 
until the news was brought in by vessels touching at 
the harbor. Earthquake shocks lasting 30 seconds 
are reported for May 20 and 23 by the keeper of 
the light at Scotch Cap on Unimak Island, and a 
'pretty severe shake' occurred at Dutch Harbor 
on June 2, but nothing is reported for April or 
March, when the new island must have risen. 
Certainly there could not have been any activity 
displayed by Makushin or Akutan, both of which 
volcanoes overlook Unalaska and Dutch Harbor, 
without being observed by the people of these vil- 
lages. Perhaps the rise of such an island, in a 
more or less plastic condition, as it must be, would 
not necessarily be attended by disturbance in the 
solid crust of the neighboring islands. On the 
Pribilof Islands, which had an origin similar to that 
of the Bogoslofs, no earthquake shock or other 
disturbance was noted, although these islands were 
affected at the time of the rise of New Bogoslof in 
1883. The Pribilof group lies 120 miles to the north 
of the Bogoslofs. 

On the whole, however, the weight of evidence 
at present seems to favor the idea that the Bogos- 
lof disturbance of 1906 was local in character and 
the coincidence in date with the California earth- 

[38] 



David 



S t a 



r r 



Jo r d a n 



quake involves no actual relation between the two 
phenomena. 

The writer first saw the islands of Bogoslof in 
July, 1896, while en route for the Pribilof Islands 




Fire Island, One of the Old Bogoslof Islands. 



in connection with the fur seal investigations. 
The U. S. Fish Commission Steamer Albatross at- 
tempted to land the commission on Old Bogoslof. 
but was prevented by the heavy surf, and the thick 
weather made only a partial view of the islands 
possible. The vessel afterwards passed the islands 

[39] 



tf k e California Earthquake of i g o 6 

on its way to the Commander Islands under more 
favorable conditions. Dr. Stejneger of the com- 
mission obtained some excellent photographs. The 
writer, still later in the same season, passed 
both islands while on the British gunboat, Satellite, 
on the way from the Russian Islands to Unalaska. 

At that time Old Bogoslof, known to the sealers 
as Castle Island, from its appearance, was cold and 
dead. It showed in the fog a sheer cliff or hill of 
ashes about 300 or 400 feet in height, seeming much 
higher in the uncertain light. It was apparently 
the home of countless sea birds and a small herd 
of the gray sea lions (Eumetopias stelleri) was hauled 
out upon one of its slopes. 

About half a mile to the northwest lay the islet 
of New Bogoslof, of about twice the height of the 
other and considerably greater area. This island 
was locally known as Fire Island, having but 
recently ceased to steam and smoke. There was in 
1896 no evidence of activity in it, but the water was 
said to be still warm in the crevices of the rocks. 
The name Grewingk, in honor of the Russian geog- 
rapher who compiled an early account of Old 
Bogoslof, has been given to this island by Mr. 
Dall. 

Both islands were surrounded with deep water. 
In fact the space occupied by the second island 
had formerly been safely traversed by vessels. 

[40] 



D a v 



S t 



J 



a n 



Dredge hauls by the Albatross about the islands 
resulted in the taking of a number of deep sea 
forms of fishes, among them three 'grenadiers' 
(Albatrossia pectoralis, Bogoslovius clarki, and Macrou- 




The New Bogoslof Island. 

rus cinereus). These were obtained at a depth of 664 
fathoms or 3,984 feet. 

Conspicuous in the group of islets was an isolated 
pillar of rock, of considerable height, known as 
Ship or Sail Rock. It had existed from the earliest 
times, having been reported as early as 1768. It 
was seen by Captain Cook in 1778, who mistook it 

[43] 



T* h e California Earthquake of i g o 6 



for a ship under sail, hence its name. This was 
eighteen years before the rise of Old Bogoslof. 
Ship Rock crumbled and fell in ruins about 1888. 
About April, 1906, midway between Old and 




Bogoslof of May, 1906. From New Bogoslof, or Fire Island. 

New Bogoslof, a third island, larger than either of 
the others appeared. Captain Dirks of Dutch Har- 
bor estimates its size as five times that of New 
Bogoslof, although the photographs do not seem 
to bear this out. This new island was first seen by 
the U. S. Fish Commission Steamer Albatross, Cap- 
tain L. M. Garrett, on May 28, 1906, while on her 

[44] 



D 



a v 



S t 



J 



d 



a n 



way to the investigation, under direction of Pro- 
fessor Charles H. Gilbert, of the fisheries of Japan. 
Soon after this date the U. S. Revenue Cutter 
Ferry visited the islands. Photographs taken by 




The Three Bogoslofs, May, 1906. 



officers of the Ferry and supplied by Mr. H. H. Tay- 
lor, of the North American Commercial Company, 
are here reproduced, together with photographs of 
Castle Island and Fire Island, taken by Mr. N. B. 
Miller of the Albatross, in 1892. 

The early history of these very interesting 
islands is given by Professor George Davidson in 

[45] 



tf h e California Earthquake of i g o 6 

the 'Bulletin of the American Geological Society/ 
Vol. XXII., p. 267, and a detailed and exhaustive 
account of them by Dr. C. Hart Merriam, profusely 
illustrated, appears in the Report of the Harriman 
Expedition of 1899, Vol. II., p. 291-336. 

Of the advent of the first island, in 1796, the fol- 
lowing account is given in Kotzebue's narrative of 
discovery in 1817. The story is that of a Russian 
trader, Kriukof, who found himself with some 
native hunters forced to seek refuge from storm on 
the north end of Umnak Island, the island of the 
Aleutian chain, nearest the Bogoslofs. It was in 
May and when the storm cleared on the 8th, Kotze- 
bue tells us: 

They saw to the N., several miles from land, a column of 
smoke ascending from the sea ; toward evening they observed 
under the smoke something black, which arose but a little above 
the surface of the water. During the night fire ascended into 
the air near the spot, and sometimes so violent, and to such 
height, that on their island, which was ten miles distant, every- 
thing could be distinctly seen by its light. An earthquake shook 
their island, and a frightful noise echoed from the mountains 
in the S. The poor hunters were in deadly anxiety ; the rising 
island threw stones towards them, and they every moment 
expected to perish. At the rising of the sun the quaking 
ceased, the fire visibly decreased, and they now plainly saw 
an island of the form of a pointed black cap. When Kriukof 
visited the island of Oomnak, a month afterward, he found 
the new island, which during that time had continued to emit 
fire, considerably higher. After that time it threw out less 

[46] 



David Starr Jo r d a n 

fire, but more smoke; it had increased in height and circum- 
ference and often changed its form. For four years no more 
smoke was seen, and in the eighth year the hunters resolved 
to visit it, as they observed that many sea lions resorted to it. 
The water round the island was found warm, and the island 
itself so hot in many places that they could not tread on it. 

The eruption of 1883, which resulted in the rise 
of New Bogoslof, seems to have had no eye-wit- 
nesses and the exact date of its appearance is un- 
known. Captain Anderson, of the schooner Mat- 
thew burner, saw the new island in September, 1883, 
and reported that great volumes of steam and 
smoke, accompanied by showers of ashes, were 
thrown out from" the summit and through fissures 
in the sides and base, the bright reflections from 
the heated interior being visible at night. At the 
time of this eruption a severe earthquake was felt 
in the sea off Cape Mendocino, apparently in the 
line of the Portola-Tomales rift of April, 1906. 

The islands were visited in 1884 by the officers of 
the U. S. Revenue Cutter Corwin, and Lieutenant 
JVC. Cantwell and Surgeon H. W. Yemans made 
the ascent of New Bogoslof. Lieutenant Cantwell 
thus describes his experience in the 'Cruise of the 
Corzcin : 

The sides of New Bogoslof rise with a gentle slope to the 
crater. The ascent at first appears easy, but a thin layer of 
ashes, formed into a crust by the action of rain and moisture, 

[47] 



T h e California 'Earthquake of i g o 6 

is not strong enough to sustain a man's weight. At every step 
my feet crushed through the outer covering and I sank at 
first ankle-deep and later on knee-deep into a soft, almost 
impalpable dust which arose in clouds and nearly suffocated 
me. As the summit was reached the heat of the ashes became 
unbearable and I was forced to continue the ascent by picking 
my way over rocks whose surfaces, being exposed to the air, 
were somewhat cooled and afforded a more secure foothold. 

On all sides of the cone there are openings through which 
steam escaped with more or less energy. I observed from 
some vents the steam was emitted at regular intervals, while 
from others it issued with no intermission. Around each vent 
there was a thick deposit of sulphur which gave off suffocating 
vapors. 

The islands were visited by Drs. C. Hart Mer- 
riam and Thomas C. Mendenhall of the Bering Sea 
Fur Seal Commission in 1891. Dr. Merriam writes 
thus of New Bogoslof as seen at that time: 

The new volcano was enveloped in steam, which issued from 
thousands of small cracks and crannies and poured in vast 
clouds from a few great fissures and crater-like openings, the 
principal of which was near the northwest corner, only a few 
feet above high-water mark. From this opening, the shape 
of which we could not see, it rushed out with a loud roaring 
noise. So great was the quantity of steam that it completely 
concealed the upper part of the island except when wafted to 
and fro by violent gusts of wind. . . . The steam was 
usually impregnated with fumes of sulphur, and deposits of 
sulphur, some in very fine needles, were observed along the 
margins of the cracks. 

[48] 



David Starr Jo r d 



a n 



Of the third Bogoslof, Dr. Charles H. Gilbert, of 
Stanford University, who was in charge of the 
work of the Albatross when the 'brand new moun- 
tain' was first seen on May 28, 1906, writes thus in 
a personal letter regarding it : 

When I saw it (Bogoslof) in 1890 there were really two 
small islands about i^> miles apart, one of them steaming and 
the other already cooled off. This has been the condition for 
a number of years, so the hot one had received the name of 
Fire Island, the cold one, Castle Island. When they came in 
sight yesterday, we were astonished to find that Fire Island 
was no longer smoking and that a very large third island had 
arisen half way between the other two. It was made of jagged, 
rugged lava and was giving off clouds of steam and smoke 
from any number of little craters scattered all over it. Around 
these craters, the rocks were all crusted with yellow sulphur. 

In a later letter, written from Yokohama, Dr. 
Gilbert said: 

I wrote you a full account of Bogoslof, but the letter seems 
to have miscarried. Our discovery seems to have been corrob- 
orated later by some revenue cutter, but if the newspaper 
report agrees with their findings, very extensive changes took 
place in the interval between the two visits. When seen by 
us, the new cone, occupying much of the space between the two 
older ones, was somewhat higher than either, but was cer- 
tainly far from 900 feet high — 300 feet would be an extreme 
figure. There was no evidence of a central crater. The steam 
and fumes were given off most abundantly from cracks and 
fumaroles on the slopes. About these were heavy incrustations 
of sulphur. We saw no indications of boiling water, nor did 
we believe that landing would be impossible. 

[49] 



*¥ h e California Earthquake of i g o 6 

In an account of the physical history of the 
Bogoslofs, written in 1899 for the report of the 
Harriman Expedition, Dr. Grove K. Gilbert, of the 
U. S. Geological Survey, noting the rapid disinte- 
gration of the islands, said: 

One might predict that in the next century the name 
Bogoslof would attach only to a reef or shoal, were it not for 
the possibility of new eruptions. The pulse of the volcano is 
so slow that we have noted only two beats in more than a cen- 
tury, but such sluggishness must not be taken as a symptom 
of death, or even decline, for volcanic organisms are charac- 
teristically spasmodic in their activity. Long before the sea 
has established its perfect sway the arteries of the mountain 
may again be opened and a new and larger island put forth 
to contest its supremacy. 

Nearly a century elapsed between the arrival of 
the first and second Bogoslof, only twenty-three 
years between the second and third. 

The floor of the depths of Bering Sea in this 
region seems to be still unsettled, and astonishing 
changes may be looked for at any time. If it should 
prove true that the geological faults of California 
extend out from this center, a new interest would 
be attached to the outbreaks of Bogoslof. 

In the fall of 1906, after the close of navigation, 
in Bering Sea, according to Mr. H. H. Taylor, of 
the North American Commercial Company, two 
violent shocks were felt at Unalaska. The people 
of that island are waiting with interest to see what 

[50] 



David Starr Jo r d a n 

new changes have taken place in the unsettled 
Bogoslof. 

The earthquake of 1906 is receiving the most 
thorough study possible, and in such a way as to 
give promise of important practical results. The 
State of California has formed an Earthquake Com- 
mission consisting of geological experts, and these 
have received in their work important financial 
assistance from the Carnegie Institution. The 
details of the earthquake rift and the effects of the 
shocks on buildings have been carefully recorded 
and photographed. The final report of this com- 
mission should leave no important question in 
doubt. Many previous earthquakes have been 
recorded in California, but their most essential 
feature, the location and extent of the causing fis- 
sure has rarely been indicated. In the records we 
read again and again that 'fissures opened in the 
ground,' but whether these were rifts in the crust 
or mere slumps of soft ground as a rule has escaped 
attention. The great earthquake of 1868 opened 
rifts at intervals from Tomales Bay to Carisa Plain, 
and also a fissure on the east side of San Francisco 
Bay, where a straight crack about ten miles long 
extended from Haywards toward the south. One 
side of this rift showed a lateral displacement of 
about four feet. To this short rift, rather than to 
the Portola-Tomales fissure, the shock in San Fran- 

[5i] 



*¥ k e California Earthquake of i g o 6 

cisco in 1868 may have been due. The shock in that 
year was more violent in Oakland than in San 
Francisco and most violent about San Leandro and 
Haywards, to the south of Oakland. It is con- 
ceivable that the shock of 1865, having its center 
in the Portola fault, not far from San Francisco, 
gave that city a degree of immunity in 1868. 
Other destructive earthquakes, as recorded by 
Holden ('Catalogue of Earthquakes on the Pacific 
Coast, 1769 to 1897') are as follows: 

1800. This earthquake was severe about San Juan 
Bautista, but whether in the Portola fault or the Pajaro fault 
is not clear. 

1812. This earthquake wrecked the mission of San Juan 
Capistrano in southern California, and was felt along the line 
of the southern missions. It had its center possibly in the 
Santa Catalina Channel. 

1818. This earthquake injured the mission of Santa 
Clara ; hence it may have been along the Portola fault. 'All the 
houses in the Santa Clara Valley were shaken down at about 
this time.' 

1836. This was said to be similar to the shock of 1868, its 
center along the Portola line ; 'great fissures were made in the 
earth.' 

1839. This was severe from Redwood to San Francisco, 
'a great fissure opened to Mission San Jose.' It was probably 
also in the Pajaro fault. 

1857. Sacramento to Fort Tejon, San Bernardino and Fort 
Yuma. At Fort Tejon 'a fissure 20 feet wide and 40 miles 
long: the sides came together with such violence as to make 

[52] 



David Starr Jordan 

a ridge ten feet wide and several feet high.' Fissures at San 
Bernardino. 

1865. This was a smart shock from San Francisco to San 
Jose, apparently along the line of the Portola fault. The 
severity of this earthquake, as suggested above, may have 
mitigated the local severity of the earthquake of 1868, which 
was in the same rift, but not so severe in this part of it. 

1867. This was violent disturbance about Klamath Lake. 
A great crack said to have opened in Siskiyou County, but the 
locality is not recorded. 

1868. A very severe earthquake, there being a rift on the 
east side of the bay, as also at Olema, in the Santa Cruz Moun- 
tains and for over a hundred miles from Cholame through the 
Carisa Plain. 

1872. Owens River, Inyo County. Fissure at Big Pine 50 
to 200 feet wide, 20 feet deep, extending 50 miles or more. 
Numerous shocks, very violent, these preceded by weaker 
shocks for a year or more. It is said that in the rift of this 
earthquake, still open, may be seen the mummified cattle which 
were engulfed in it in 1872. This statement is given on the 
authority of Mrs. Mary Austin. 

1890. Mono Lake, similar disturbances. 

1892. Vacaville, Winters, etc., extensive local disturbances, 
the fissures not traced, but said to have been along Rio de los 
Putos on the west side of the valley of Solano and Yolo. This 
rift extends through the volcanic basin of Clear Lake to the 
northward, parallel with the Tomales fault. 

1897. San Jacinto Valley, with a notable fissure, the details 
not at hand. 

To these might be added the vigorous single 
jolt of 1893 in the San Fernando Mountains, which 
did little harm because occurring in an unhabited 

[53] 



T ' h e California Earthquake of i g o 6 

region. The writer was at Saugus at the time, 
and noted the fall of trees and the flinging of rocks 
down the mountainside. There seems to have been 
but a single wave, which would have done great in- 
jury in a populous district. It is said to have arisen 
from a short fissure in Pico Canon. 

Since the earthquake of 1906 many small earth- 
quake waves have followed, evidently harmless de- 
tails in the process of adjustment. Looking over 
Holden's record, we see that many small disturb- 
ances have taken place along the line of the great 
fault in question, besides the great earthquakes of 
1868 and 1906 and the lesser ones of 1800, 1818, 
1836, 1839, 1865 and 1868. 

In 1808 there were twenty-one shocks at the 
Presidio of San Francisco. In 1812 the shocks 
caused a tidal wave in the bay extending up to the 
plaza. In 1813 or 1815 'all the buildings' in Santa 
Clara Valley were shaken down. There were not 
many and all these were of adobe or sun-dried 
brick. In 1851, a sharp shock in San Francisco. 
In 1852, a shock at San Francisco, with a fissure, 
through which Lake Merced drained into the sea. 

1853. Heavy shocks near Humboldt Bay. 
1856. Severe shocks at San Francisco, the water in the bay 
sank two feet. 

1863, 1864. A sharp shock at San Juan Bautista. 

1890. Sharp shock along Portola fault. The Pajaro bridge 

[54] 



David Starr Jordan 

had a pier shifted 18 inches, as in 1906. The same crack 
opened at Chittenden, and the main arch in the Mission Church 
at San Juan Bautista was injured. A rift opened in the soil 
from Chittenden to San Juan as in 1906. 

Ill a general way this seems to be proved with- 
out question: The great earthquakes in non-vol- 
canic regions occur always in the same rifts. They 
also occur with a certain sort of periodicity. The 
Portola rift with its destructive earthquakes of 
1812, 1836, 1868 and 1906, seems to have a period 
of thirty to forty years. In the intervening time 
the region of this rift may be reasonably regarded 
as immune.* 

The same sort of periodicity, with an interval of 
about 30 years, has been noticed in the seven earth- 
quakes of Chile. 

These great semi-periodical earth-changes are 
known in Spanish speaking countries as terramoto. 
It is the minor waves which the Spaniards call 
te?nblor. 

We may again emphasize the fact that the 
earthquakes of California are purely mechanical in 
their origin. The coast, for some reason connected 
with the secular changes in continents and seas, is 
in California and along the whole run of the Pacific 
slowly rising. Perhaps some part of the Pacific 
Ocean is slowly sinking, as part of the same move- 
ment. In any event, the rise of this heavily loaded 

[55] 



C Z J h e California Earthquake of i g o 6 

and much broken area is accompanied by a heavy 
strain. This the break in the rocks apparently re- 
lieves, and when the strain reaches a certain point 
it will break again, and this at more or less regular 
intervals. 

The earthquake at Valparaiso seems to have 
been caused by the same kind of a strain operating 
in the same way. As a final result of it the whole 
coast of Chile has been elevated. 

While many slumps and breaks in the land have 
been noted in Chile, there is no continuous rock-rift 
or fault like that shown by the California earth- 
quakes. Undoubtedly the rift was in the sea, and 
probably parallel with the line of the coast. 

The tremendous earthquakes of a few years ago 
in Alaska, along the foot of Mount St. Elias and 
Mount Fairweather, earthquakes which wrecked 
the Muir Glacier and altered that of Malaspina 
must have been of the same nature and origin. 
Similar strains on the same strained ocean-rim 
probably caused the Bogoslof disturbances, and 
Jamaica is not so far from the Pacific that it may 
not be included in the same circle of disturbance. 
The Asiatic side of the Pacific is still more unsteady 
as a foothold for man. Japan, Formosa, and the 
Philippines are notoriously subject to earthquake 
rifts as well as to volcanic outbreaks. The islands 
of the straits of Sunda have a world-wide reputation 

[56] 



David Starr Jordan 

in these regards, and if press statements are accu- 
rate, there have been of late great disturbances in 
the Solomon Islands. As most of the islands of 
Polynesia and Micronesia are volcanoes, or of vol- 
canic origin, disturbances in these regions need 
not cause surprise. 

In the California earthquakes there are no ex- 
plosions, no bursting of 'caves of gloom,'' no escape 
of sulphurous or other gases, and none of the phe- 
nomena real or alleged which excite the imagination 
of the superstitions of the ignorant or credulous. 
They are not caused by electricity nor accompanied 
by electrical disturbances. Electricity is a mighty 
force only when held in great tension by some form 
of insulation. Land and sea, unlike storm clouds, 
offer no means of electrical insulation, and electrical 
tension cannot be accumulated along the sea bot- 
toms where so many earthquake disturbances occur. 

The electrical theory of earthquakes is thus 
intelligibly given by Mr. Charles Hallock, the ac- 
count being a condensation of his views as stated 
in an article called 'Polarity of the Seismic Im- 
pulse': 

Accepting the theory of Sir Oliver Lodge and 
other advanced scientists of eminence, that the 
earth is a magnet, and its crust simply the arma- 
ture of an immense dynamo whose source is the 
sun, Mr. Hallock attributes the unusual prevalence 

[57] 



*? k e California Earthquake of i g o 6 

of earthquakes, and the manifest sympathy be- 
tween so many of them, to the earth being sur- 
charged with electricity. This redundant voltage 
sets in motion the loose heterogeneous masses of 
which the terrene envelope is so largely composed, 
and these in turn generate electrical energy. This 
is in line with Clerk Maxwell's showing, the rock 
and earth movements being facilitated by exces- 
sive rains which saturate and lubricate the dis- 
located masses. Jarring is often maintained for 
weeks and months at intervals, after the initial 
shocks, in obedience to the law of adjustment 
which causes disintegrated particles to settle and 
become compact. 

Mr. Hallock goes on to aver that all our troubles 
and calamities are not due to natural causes alone, 
but that men's dabbling with electricity, to the 
extent of gridironing nearly the entire globe with 
wire conductors, overhead and underground, in the 
atmosphere and through the oceans, and in prac- 
tically every house in town and country, and keep- 
ing them constantly charged by powerful dyna- 
moes, is the stimulating cause of current perturba- 
tions, landslips and volcanic eruptions, which are 
far in excess of any known period since the Terti- 
ary. All of which he takes occasion to remind us is 
predicted in the book of Isaiah, which declares 
that 'men shall be plagued by their own inventions.' 

[58] 



David Starr J o r d 



a n 



It is clear that this view does not account for 
the conditions in California. The great earthquake 
rift follows the line of a fault which shows clearly 
traces of many earthquakes before any men lived 
in California. There is no evidence that the recent 
earthquake was any more severe than those of 1836 
or 1813. It is much less severe in San Francisco 
than anywhere along the rift in Marin or Mendo- 
cino Counties. It was even less severe in San 
Francisco than along the possible secondary rift 
in Sonoma County. It is perfectly clear that the 
operations of man at San Francisco had nothing 
to do with the rift of rock in Marin and Mendocino 
Counties, nor with its extension in 1868 along the 
line of Cholame and the Carisa Plain. 

No one can check an earthquake or modify its 
action. There is no lightning-rod insurance against 
it. Fortunately also no one can set it off or stim- 
ulate it to any greater violence than nature has 
intended. 

There is no reason to suppose that any planetary 
conditions produce earthquakes. The conjunction 
of the planets, even all of them, would produce less 
variation in strain than the conjunction of the sun 
and moon which occurs every month. That is 
adequate to produce variation in tides, but scarcely 
enough to be detected by the finest balances. A 
force too small to be weighed is scarcely likely to 

[59] 



T* k e California Earthquake of i g o 6 

shift mountains, though it is conceivable that it 
might set them off, under conditions like that of 
the proverbial last straw on the overstrained camel. 
There is no evidence of connection between earth- 
quakes and sunspots. They may appear coincident. 
The sun is seldom without spots and there are few 
years without a destructive earthquake on some 
part of the earth's surface. Little tremors of one 
sort or another occur somewhere or other every 
hour, and the crust of the earth is never quite at 
rest. 

There is no evidence of connection of earth- 
quakes with any kind of climatic condition. The 
notion of 'earthquake weather' is an absurd super- 
stition. Earthquakes have no preference for any 
month, for any time of the day. Wet ground 
slumps more than dry ground, but the wetness is 
not a cause of the earthquakes. They cannot be 
predicted except in the most general way, as I 
might say, the next earthquake at San Francisco 
is due in forty years, namely in 1946. Soothsayers 
and clairvoyants being vulgar, ignorant and preda- 
tory persons of criminal instincts know not more 
but less about earthquakes than the average decent 
citizen. 

Moreover, it is no longer believed that the wick- 
edness of man produces earthquakes. This has 
its own reward, but the sin and the penalty are 

[60] 



David Starr J o r d a n 

like in kind. The mountains break as an over- 
weighted leaf of a table would break when the 
strain is growing greater and it can be borne no 
longer. 

The earthquake of 1868 was far less violent than 
that of 1906, along the San Francisco peninsula, 
although it extended farther to the south than the 
other. It may be remembered that the population 
of the region is now much greater than in 1868, 
and in like manner, the possibilities of mischief on 
the part of earthquakes has been correspondingly 
increased. The danger from earthquake itself is 
relatively a small matter, but it should be con- 
sidered in the building arrangements of regions 
where such disturbances are likely to recur. It is 
as easy to make buildings virtually earthquake- 
proof as water-proof, unless standing directly over 
the fault itself. Earthquake-proof structures can 
be made of steel or of properly mixed concrete, 
properly reinforced by steel, or within certain limits 
of brick or stone firmly cemented and with roofs 
properly made and properly tied together. Brick 
and mortar are not adequate for the existing con- 
ditions of California. . A firm foundation is more- 
over of primary importance. In loose soil, and 
especially in sand, earthquake waves are much 
higher, longer, slower and more destructive than 
in rock. In this connection we may close with the 

r 6i i 



tf h e California Earthquake of i g o 6 

pertinent words of the engineer, William H. Hall, 
of San Francisco: "The earthquake has put a def- 
hnition on the word sham, which seems positively 
cruel. It has established a value on the solid foun- 
dation and genuine superstructure which is indeed 
ennobling." 

It would redound to the moral and spiritual ele- 
vation of any community to be assured of a smart 
shock or temblor at intervals and of a real earth- 
quake or terramoto once in each generation. 



62 



Geology and the Earthquake 

By 

John Casper Branner 

Vice- Preside fit and Professor of Geology at Stanford University 



Geology and the Earthquake 



WHAT is it? What causes it? Where does 
it come from? Will it happen again? and, 
if so, when and where and how much? 
These are the questions the geologist is expected 
to answer regarding earthquakes in general, and 
in particular regarding the California earthquake 
of April 18. And, as usually happens in such 
cases, the geologist can half answer some of these 
questions, and others he can not answer at all. 

To begin with the last item — the "how much?" 
Was the late earthquake really a severe one, or was 
not its severity and importance greatly exagger- 
ated as compared with great earthquakes, and was 
not this exaggeration carried still further by the 
burning of San Francisco, which immediately fol- 
lowed? 

The scales in use among geologists for classi- 
fying earthquakes divide them into ten classes, ac- 
cording to their violence or intensity. By the 
Rossi-Forel or the Mercalli scales, the Califor- 
nia earthquake stands somewhere between eight 
and ten at points of greatest disturbance; from 
which we infer that we may trust our senses to the 
extent of believing that it was no small affair. 

[65] 



tf h e California Earthquake of i g o 6 



The picturesque and sensational features of 
earthquakes are abundant and entertaining, but to 
the geologist these features have only a passing 





\ •./ 








-. 


"^***F&:f 






H 




*fe M mj& <jl„. 


fcT'^s'. ■";■■■ "' 


- 


i 


i ■■-■■■:. 


•■■ •• - - -. ' •"' 




He/ r; '""'•■" 


" 


' ' • . '■'n : ##-' / ^;./ ■*■ " 


Jfe 









Slump in Soft Ground, Milpitas. 

and accidental interest. For example, if a chimney 
top, broken off by an earthquake, should fall on a 
man in such a fashion as to go right over his head 
and leave him standing unhurt in the flue, it would 
be a striking, and to the man a very important, 
fact; but, from a geological point of view, its only 
importance would lie in the fact that the shock was 
severe enough to throw down the chimney. One 
hears, in the vicinity of Palo Alto, of a herd of 
cattle having been swallowed up in the Santa Cruz 

T 66 1 



J 



h n 



C a 



B 



a n n 



Mountains and how they had to be dug out. This 
seems like a genuine earthquake tragedy; but it 
turns out that at the time of the earthquake there 
was a landslide affecting some ten acres of land 
on which the herd was grazing. On the higher 
side, the slide left banks up which the cattle could 
not climb, so that a road had to be dug to get them 
out. This again turns out to be a matter of but 
little importance from the geologic point of view. 
Mention is made of such cases simply to call atten- 




Rift Crossing Road near Skylands, Santa Cruz County, Showing 
Relative Sinking of West or Uphill Side of Rift. 



tion away from the strange and bizarre, and to 
direct it more effectively to what are regarded as 
matters of fundamental importance in connection 

[67] 



< f h e California Earthquake of i g o 6 

with earthquakes. The phenomena that bear 
directly upon the causes and throw some light upon 
the past and future seismic history of the region are 
evidently the ones of the deepest importance, and it 
is to some of these that attention is directed. 

In the Portola Valley, five miles west of Stanford 
University, there runs through a pasture field what 
looks like a plowed furrow. It is such a furrow as 
might be made by a big turning-plow, except that 
the sod is not turned clear over, the clods and 
grass roots are rough and irregular, and the furrow 
not straight or gently curved, but ragged and 
lumpy and sometimes forked. Where this furrow 
crosses a fence-line, the fence has an offset in it 
amounting to a little more than eight feet. A few 
hundred yards away, it crosses another fence-row 
at a low angle and here there is eight feet more 
then is now needed; where it crosses a third fence 
at a right angle there is another offset in the fence 
of fully eight feet; at another place it crosses a line 
of water-mains, and the pipes are displaced more 
than six feet. 

To the passing observer these facts may appear 
trivial enough, but to the geologist they are full of 
interest and importance, for they lie close to the 
source of the earthquake; they are produced by a 
lateral displacement along a line of fracture in the 
crust of the earth. Where this fracture passes 

[68] 



C a 



B 



a n n 



through the Santa Cruz range of mountains, it was 
worked out from the geology some ten or fifteen 
years ago and was gradually traced in detail for 
a distance of forty-five miles. Starting on the 
coast at Mussel Rock, seven-and-a-half miles south 




Rift Across Road near Azul Springs, Santa Clara County. 



of the Cliff House, it takes a course of south about 
40 degrees east, following certain topographic fea- 
tures that are plain enough on the ground. It runs 
through San Andreas and Crystal Springs Lakes, 
Portola Valley, passes just west of the peak of 
Black Mountain, follows along Stevens Creek 
Canon, and, passing to the west of Loma Prieta, 

[69] 



< f h e California Earthquake of i g o 6 



continues in the direction of Sargents Station on 
the Southern Pacific Railway. 

Immediately after the recent earthquake this old 
line of fracture was visited at a number of places 
and everywhere it showed evidence of having been 




House over Rift near Saratoga Springs, California. 

newly broken and displaced. The displacement 
was mostly a lateral one, amounting to a maximum 
of eight-and-a-half feet, but there was also some 
vertical movement which probably does not exceed 
three feet in the region thus far examined. The 
country southwest of the fault sank and moved at 
the same time toward the northwest, or else the 
region on the opposite side rose two or three feet 

[70] 



John Casper B r a n n e r 

and moved about eight feet toward the southeast. 
When we reflect that these mountain masses were 
moved such a distance in a few seconds and stopped 
suddenly, there is no cause for wonder at the jar 
produced in the adjacent region. 

The materials visible in the line of this fault 
are worthy of note. The fault is an old one, along 
which many and great movements have taken 
place; the rocks have therefore not only been 
broken across, but they have been crushed, re- 
crushed and ground up until it is now difficult or 
impossible to find large blocks close to the fault- 
line. Furthermore, the word "line" is here some- 
what misleading, for it is really a belt or zone, from 
twenty to fifty or one hundred feet across, rather 
than a clean-cut line or plane. At the surface, de- 
composition has further attacked the materials and 
the soil is commonly deep and yielding and this soil 
has in all probability taken up a good deal of the 
actual displacement by lagging, stretching and 
crushing; this seems to account for the fact that 
the displacement is not everywhere of the same 
amount. 

The phenomena to be seen at the surface along 
this line of displacement are such as might be ex- 
pected. Wherever fences cross the fracture at 
right angles they are torn in two and the broken 
ends now stand from one to eight feet apart; roads 

[7i] 



C T h e California Earthquake of i g o 6 



that were formerly straight are now bent; barbed- 
wire fences are pulled in two or they are variously 
shortened; water-pipe lines have the pipes either 
broken and pulled apart, or where the pipe line 
crosses the fracture at a low angle the pipes are 




Redwood Snapped Off by Earthquake near Fort Ross, Cal. 

telescoped into each other from four to six feet. 
A dam across Crystal Springs Lake crossed this old 
fault-line at right angles; it was expected that the 
dam would be torn in two or badly fractured, but 
it was so well built that the fault was compelled 
to pass round the dam and through the rocks at its 
end. The same thing happened at the dam across 
the east end of San Andreas Lake. Where trees 
stood directly upon the break they have been up- 

[72] 



John Casper B r a n n e r 

rooted, and in some cases they have been split in 
two. 

Such are a few of the evidences of a displacement 
of the rocks over a distance of some seventy-five 
miles through the Santa Cruz Mountains south of 
San Francisco. North of that city the topography 
suggests that this same, or a closely related, fault 
passes through Tomales Bay, down the Gualala 
and Garcia Rivers, entering the ocean at the town 
of Manchester near Point Arena light-house. It 
is expected that a further examination will disclose 
similar evidences of displacement along this line 
north of San Francisco. 

The fault-line mentioned, however, is far from 
being the only one in the Coast Ranges. The long 
parallel valleys of the State are due, in part at least, 
to faulting that took place a long while ago. One 
great fault, that seems to have been involved in the 
California earthquake, follows the entire length 
of the Santa Clara Valley, from about the head- 
waters of the San Benito River south of Hollister, 
past San Jose, through the Bay of San Francisco, 
up the valley past Santa Rosa, Ukiah, Willits and 
down the Eel River, or parallel with it, to Eureka 
in Humboldt County. Since the earthquake, this 
fault-line has not been seen by the writer, but many 
cracks have opened along its axis near the south 
end of the Bay of San Francisco between Milpitas 

[73] 



*? h e California Earthquake of i g o 6 

and Alviso. At this place not only were cracks 
opened from one to four feet wide and five or six 
feet deep in the soil, but for a couple of days water 
ran out through some of the cracks bringing up 




The Fault Passes Under a Live Oak and Uproots It, Woodside, Cal. 

sand and forming small cones about them. Some 
wells began to overflow that hitherto had never 
done so, the flow in other wells increased very de- 
cidedly, while in still others the water sank some- 
what. 

Evidently the earthquake and the faults are re- 
lated; but did the faults make the earthquake, or 
did the earthquake make the faults? It is a fair 

[74] 



J 



c 



p 



B 



r a n n 



question. Look at the matter for a moment from 
a purely theoretical point of view. Conceive of a 
mass of rock as big as a big house under pressure 
enough to break it — would not the breaking pro- 




Rift on Shafter's Ranch, Olema, Cal. 

duce a jarring of the surrounding mass? Or imag- 
ine such a rock already broken across and the two 
faces forced past each other for a distance of eight 
feet — would not this movement jar the surround- 
ing mass? And if the break were three hundred 
miles long would not the jar extend into the ad- 
jacent rocks and soil in the same fashion and for 
many miles? This theory seems to explain the 
earthquake. 

[75] 



T* h e California Earthquake of i g o 6 

There are fractures, however, that evidently 
must be attributed to the earthquake; such are 
those connected with landslides, the disturbance of 
steep and unstable slopes, the settling of loose 
masses of gravels and the like in wet ground. But 
these are all matters of small importance and quite 
incapable of producing earthquakes, except of a 
very local kind. 

It is plain enough that faults are caused by un- 
equal pressure developed in the rocks. This pres- 
sure may bend the rocks, or it may break them and 
thrust them past each other; and when they break, 
the fractures may pass down for thousands of feet, 
or even for miles, into the rocks beneath the sur- 
face. What causes this strain or inequality of 
pressure is not so evident. Three theories have 
been suggested: first, the cooling and consequent 
contraction of hot rocks; second, the heating and 
consequent expansion of cool rocks; third, the shift- 
ing of loads upon the earth's crust by the washing 
of land-masses into the sea. 

But whatever theory one adopts regarding the 
remote causes of earthquakes, the conclusion is in- 
evitable that they are produced by natural causes, 
one of which is the relief of strains within the earth's 
crust along lines of fracture. The knowledge that 
they are due to natural causes ought to contribute 
to a philosophical view of them and rid them to 

[76] 



John Casper B r a n n e r 

some extent of the terror they inspire in the minds 
of those who attribute them to the wrath of God 
or to other supernatural causes. 

As for the earthquake happening again, the only 
guide the geologist has is the record found in the 
rocks. This record shows plainly enough that there 
always have been earthquakes. As for anything 
more specific in regard to time and place and 
violence of future earthquakes, the geologist must 
leave prophecy to the prophets. 



[77] 



The Destructive Extent of the Cali- 
fornia Earthquake. Its Effect 
Upon Structures and Structural 
Materials Within the Earth- 
quake Belt 

By 

Charles Derleth, Jr. 

Associate Professor of Structural Engineering, University of California 



The Destructive Extent of the 
California Earthquake 



ON the eighteenth of April, 1906, at 5:13 in 
the morning, one of the most severe earth- 
quakes ever recorded since the beginning 
of civilized habitation visited the State of Cali- 
fornia. The important destruction to engineering 
works occurred in a belt about fifty miles wide and 
nearly three hundred miles in length, extending 
along the Pacific Coast, with the Bay of San Fran- 
cisco at its center. 

INTRODUCTION 

Immediately after the earthquake the Governor 
of California, the Hon. George C. Pardee, estab- 
lished the California Earthquake Investigation 
Commission, which has diligently studied the 
scientific phase of the subject. The commission's 
preliminary report clearly outlines the general 
geological features of the earthquake belt and the 
important phenomena observed in the region of 
most violent shock. The commission has carefully 
studied time records to determine coseismal curves, 
and collected data for the purpose of establishing 
lines of equal severity or intensity of shock, that is, 

[81] 



C T h e California Earthquake of i g o 6 

isoseismal curves. As one of the conclusions to 
their work the commission will undoubtedly dis- 
cuss the relation of earthquake effects to man and 
to human works, that is, engineering construction; 
but as that body consists mainly of pure scientists, 
namely, geologists, physicists, and astronomers, 
their work in the interpretation of the destruction 
to structures can not be complete without the co- 
operation of students of engineering. 

Members of the San Francisco Association of the 
American Society of Civil Engineers have consid- 
ered the engineering side of this large problem, and 
various sub-committees have reported detailed 
studies for different and distinctive types of con- 
struction, such as buildings, streets, harbor works, 
water systems, sewers, railroads, power stations, 
and foundations. These reports have been for- 
warded to the parent society in New York and have 
been printed in the March (1907) Proceedings of 
the American Society of Civil Engineers. 

A local association given the name of the "Struc- 
tural Association of San Francisco/' consisting of 
engineers, architects, contractors and manufac- 
turers of structural materials, with a purpose sim- 
ilar to that of the American Society of Civil Engi- 
neers, is also in the field. Its members, too, have 
appointed sub-committees for a division of labor in 
collecting and studying data in this vast problem. 

[82] 



Charles D e r I e t h , Jr. 

The Structural Association is confining its atten- 
tion mainly to San Francisco and the question of 
earthquake-proof and fire-proof buildings. 

At this writing a report is in press, written for 
the United States Geological Survey by Messrs. 
John S. Sewell, Frank Soule and Richard L. 
Humphrey, in which these gentlemen, all engineers, 
treat of the effect of earthquakes and fire upon 
structural materials. 

Furthermore, many articles by engineers have 
appeared during the past year in the engineering 
journals, treating of the earthquake and fire 
problems. It is plain, therefore, that the subject is 
receiving considerable attention by those interested 
in building and in structural materials. 

Engineers are concerned not only with the tem- 
blor's destruction, but also with the fire problem. 
Immediately after the earthquake, great conflagra- 
tions broke out in San Francisco and Santa Rosa. 
The earthquake meted out great destruction, and 
the large losses will be felt for some time to come; 
but there is always at least a little good accompany- 
ing evil, and all intelligent and honest builders have 
recognized that the calamity offers a great oppor- 
tunity to compare the efficiencies of different types 
of design and to observe the relative behavior of 
different kinds of materials in their resisting quali- 
ties to withstand earthquake shock and retard the 

[83] 



T 'he California Earthquake of i g o 6 

progress of fire. It seems to me that the engineer- 
ing problem is at least as large as that of the geol- 
ogist; at any rate it is more important in its prac- 
tical bearings, because it combines the study of 
structural stability with the theory of fire-proofing 
and must pay considerable attention to the relation 
of destruction of structures to geological forma- 
tions. 

From the purely scientific standpoint this earth- 
quake presents perhaps the most favorable problem 
which it has yet been the privilege of seismologists 
to study, because the extent of the earthquake is 
so large, the area of destruction embraces such 
varied topography, and because the geological 
formations of the Pacific Coast are so striking and 
so unique. From the very first, the center or line 
of disturbance has not been in doubt, for a crack is 
visible on the earth's surface for at least 200 miles, 
and runs in an almost unbroken straight line along 
an old geological scarp. This scarp, or plane of 
crustal weakness, is plainly visible to the educated 
geological eye, and has been known to geologists 
for more than a generation. Again, the magnitude 
of the shock was so considerable that its vibrations 
were felt at many places quite remote from San 
Francisco. The tremors were distinctly felt in the 
southern part of California, in Oregon, and at sev- 
eral places in Nevada; while precise instruments 

[84] 



Charles D e r I e t h , Jr. 

have recorded small crustal movements at Wash- 
ington, D. C, in Germany, and at Tokyo. We 
have here a fruitful opportunity for an advance in 
the world's knowledge of geophysics, and scientists 
generally will look with anticipation to the final 
report of the California State Earthquake Com- 
mission. 

For the engineer, from the purely applied science 
point of view, there is an equally wide opportunity. 
All kinds of construction and all kinds of material 
have been subjected to both stress and fire. Struc- 
tures, good and bad, of able and deficient designs, 
of honest and criminal workmanship, all have been 
tested by various degrees of vibration, from the 
most severe shocks in the region of the fault line to 
shocks of much less severity for places resting upon 
firm foundations. 

EARTHQUAKES AND CRUSTAL MOVEMENTS 

The crust of the earth is constantly adjusting 
itself to conditions of stress and strain. The sur- 
face of the globe is gradually and slowly changing 
its form to suit these adjustments. The span of a 
human life is quite negligible in comparison to the 
geologic ages required to bring about marked defor- 
mations in the surface of the globe, and conse- 
quently many of us are not aware of the slow 
crustal movements which to the eye of the experi- 

[85] 



tf h e California Earthquake of i g o 6 

enced geological observer are everywhere in evi- 
dence upon the world's surface. 

Some parts of the earth's crust are slowly sink- 
ing; a portion of the east coast of the State of New 
Jersey is said to be dropping. In other places the 
land is rising; it is claimed that the coast ranges 
in California are young mountains pushing their 
way through the coastal plain. Many such state- 
ments for different parts of the surface of the globe 
may be cited. These are effects of the so-called 
mountain-making or tectonic forces which act 
through long periods of time and over wide areas. 

Some parts of the earth's surface are more set- 
tled or stable than others, and we do not expect 
severe crustal movements in such regions. New 
York City, resting on strong elastic rocks, is prob- 
ably an example. The Adirondacks and vicinity, 
whose foundation is of the earliest geologic age, 
is never associated with earthquakes. In other 
places, crustal movements, that is earthquake phe- 
nomena, are from time to time to be expected. Japan 
and the Pacific Coast of America are such coun- 
tries. As the earth's crust gradually changes, lines 
of weakness no doubt will be shifted from one part 
to another of the globe's surface, and what are now 
termed "earthquake countries" may no longer be 
so in the next geologic age. 



[86 



Charles D e r I e t h , Jr. 

I must distinguish between the volcanic and tec- 
tonic earthquakes. In the present discussion it is 
not necessary to consider the volcanic type. Vol- 
canic earthquakes are generally local and their ef- 
fects of smaller extent. They are comparatively 
rare. The tectonic or mountain-making earth- 
quakes are more frequent in occurrence; they may 
affect large surfaces on the globe, as in the present 
instance; they may be severe, or so slight that 
only the most delicate seismic instruments will de- 
tect them. For a year previous to our great April 
earthquake, shocks were recorded by delicate in- 
struments with great frequency in the neighbor- 
hood of San Francisco. While tectonic earthquakes 
are apt to occur more often in regions of proved 
crustal weakness and instability, they are neverthe- 
less liable to occur anywhere and at any time. 

The crust of California, dynamically speaking, is 
alive and active. Here the earth's surface is in 
growth and we are witnessing one instant perhaps 
in its development. Geologically speaking, the 
earth's crust in California is somewhat unsettled 
or unstable, and I see no object to be gained by 
not admitting this fact. Earthquakes are natural 
phenomena and should not be feared. We can not 
contend with nature's forces, but we certainly can 
try to adjust ourselves and our works most favor- 
ably to their requirements. Earthquakes offer to 

[87] 



The California Earthquake of i g o 

the geologist most interesting dynamical problems, 
and their effects upon human construction, no mat- 
ter how unfortunate, lend to the engineer and the 
artisan most valuable experience and counsel. 

FAULT LINES IN CALIFORNIA 

More than a generation ago geologists mapped 
out long continuous fault lines upon the face of 
California. These lines are the results of former 
slippings or accumulations of slips that have oc- 
curred in the past, often the remote geological 
past, and thorough study reveals their relation to 
California topography. Most of these important 
fault lines, if not all, run in a general north-north- 
westerly direction, essentially parallel to the moun- 
tain range lines, a parallelism which is quite nat- 
ural and to be expected. A study of the report of 
Mr. G. K. Gilbert, Monograph 1, U. S. Geological 
Survey, describing the phenomena at Lake Bonne- 
ville, and the earthquake destruction in Inyo 
County, California, in 1872, also the work by Pro- 
fessor Andrew C. Lawson entitled "Sketch of the 
Geology of the San Francisco Peninsula," Fifteenth 
Annual Report, U. S. Geological Survey, page 405, 
will fully acquaint the reader with the geology of 
California and help him the better to appreciate 
what happened on the eighteenth of April, 1906. 



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Charles D e r I e t h , Jr. 

The great earthquake of 1872 was accompanied 
by and was coincident with heavy slipping along 
parts of a pronounced fault line which traverses 
the western flank of the Sierras from Owens Lake 
in the south toward Lake Tahoe in the north. A 
relief map of the San Francisco peninsula given by 
Professor Lawson in the work above referred to, 
see Fig. 1., shows clearly a part of another great 
fault line which follows the coast and runs in the 
same general direction as the one in the Sierras. 
This great coast fault is clearly shown by the map, 
Fig. 1, to run through Lakes San Andreas and 
Crystal Springs of the Spring Valley Water Com- 
pany. There are a number of lesser faults to be 
studied in the coast range region. These faults are 
lines of weakness in the crust along which move- 
ments and slippings have occurred in the past; and 
renewed ruptures or movements in the rocks far 
below the surface, at the same time that they pro- 
duce earth vibrations, may also cause surface 
cracks and other evidences along these geological 
scarps, — effects which were so pronounced in 1872 
in Inyo County, and this time in the coast ranges 
near San Francisco. 

THE MAIN COAST RANGE FAULT 

The earthquake of April eighteenth has affected 
the crust and the surface of the ground along the 

[9i] 



T h e California Earthquake of i g o 6 

main coast range fault. This fault or rift, Fig. 2, 
runs in an almost exact right line from Point 
Arena in the north, following along the coast 
through structural valleys or bays in a south-south- 
easterly direction, to Hollister in the south. Above 
Point Arena it disappears into the ocean, although 
there is some evidence that it curves to the east 
and approaches the land in the region of Cape Men- 
docino. This is probably the case; at any rate it 
would explain the considerable shock felt in Hum- 
boldt County. To the south of Hollister the fault 
may be traced by the observing eye along the west- 
ern side of the San Joaquin Valley and into the 
desert lands to the south; some say almost to the 
head of the Gulf of California. As to the exact 
location and limit to the fault line in the south I 
can not speak definitely. I have not examined that 
region nor does the question of southerly extent 
really concern the engineer in this present earth- 
quake problem. I have followed the rift from Point 
Arena to the region of Hollister and Tres Pinos. 
In this length of a little more than 200 miles the 
ground along the fault line was broken, and consid- 
erable horizontal and some vertical movement oc- 
curred throughout that distance. Movement and 
faulting below Hollister, if there was any, was 
slight, and I have heard of no authentic reports. 
Below Hollister, moreover, there is little improved 

[92] 




Fig. 2 — Map of California, Showing Position of Fault Line, 
Earthquake of 1906. Reprinted from "Engineering News," June 
28, 1906. 



Charles D e r I e t k , Jr. 

property and therefore hardly anything of en- 
gineering importance to destroy. Along the fault 
from Point Arena to Hollister the earthquake des- 
truction was most severe. Water pipes, conduits, 
bridges, fences, roads, water courses, all things 
that crossed the line were crippled or rent asunder. 
In the north, trees were uprooted, broken and 
cracked, and everywhere along the fault buildings 
of weak construction were violently thrown down. 

THE BELT OF MAIN EARTHQUAKE DISTURBANCE 

The belt of great disturbance may be said to 
extend somewhat to the north of Point Arena into 
Humboldt County, and perhaps somewhat to the 
south of Hollister and Mt. Pinos, a distance of 300 
miles or more. The disturbance was keenly felt 
for considerable distance to the east and west of 
the fault line, and a width of fifty miles may be 
assigned to the belt of great destruction. Within 
this belt will be found all the important examples 
of earthquake destruction to engineering works. 
It is plain that the extent of the seisma is large. 

EFFECT OF TOPOGRAPHY AXD GEOLOGICAL STRUCTURE 

Within this belt, as I have already stated, the 
most severe racking of structures occurred right on 
the fault line, the most striking examples being the 
Pilarcitos conduit and San Andreas dam of the 

[95J 



tf h e California Earthquake of i g o 6 

Spring Valley Water Company of San Francisco, 
and the Pajaro River bridge on the Southern Pa- 
cific Railroad near Chittenden Station, where the 
railroad crosses the Pajaro River. These struc- 
tures, though well designed, were much racked or 
even ruined, as in the case of the Pilarcitos conduit, 
because of the large and unequal movements of the 
ground along the rift. The intensity of shock, 
however, is observed to have varied greatly, and 
well-built structures which rested on hard and 
rocky surfaces were relatively little damaged. 
Rocks and the structures resting upon them were 
shaken by an elastic vibration without differential 
movement, and whenever the construction was in- 
telligent and honest it withstood the shock. There 
are many examples of buildings of such behavior 
on rocky summits in San Francisco. Compara- 
tively little destruction was meted out in cities 
like Santa Cruz, San Rafael and Berkeley, which 
rest on rocky foundation, or other sound coherent 
materials. 

Within the belt of great destruction are found 
many localities or spots where considerable dif- 
ferential surface movement occurred, though at 
considerable distances to either the east or the 
west side of the rift. Examination shows such 
localities to be overlaid with loose incoherent ma- 
terial. In one place we find a loose river deposit, 



Charles D e r I e t h , Jr. 

in another a marsh, and in a third an artificial fill. 
Examples of destruction in such localities are 
found (1), near Salinas, where the Spreckels 
Sugar Mill, a first-class steel cage constructed 
building, was much racked; (2), in the San Bruno 
marsh, near South San Francisco, where the Crys- 
tal Springs conduit of the Spring Valley Water 
Company was smashed; and (3), on the filled 
ground areas of San Francisco in the Mission 
District and along the water front near the Ferry 
house, where the street surfaces were deformed 
into billow-like waves, and structures with weak 
foundations were generally destroyed. In all 
these cases the differential motions were of a sec- 
ondary nature and not directly connected with the 
movements along the fault line. The vibration of 
the earth's crust caused marshes which were near 
to the center of the disturbance to shake like bowls 
of jelly, and loose sandy and alluvial deposits and 
artificial dumps and fills were much shifted and 
shaken about upon the firmer ground beneath 
them. 

A line of considerable but lesser intensity of 
shock may be traced approximately parallel to the 
fault line through the bottom lands of the valleys 
which contain Santa Rosa and Healdsburg in the 
north, and Agnews and San Jose in the south, 
with the Bay of San Francisco as a central feature. 

[97] 



tf h e California Earthquake of i g o 6 

These bottom lands are alluvial deposits of soft and 
considerably incoherent materials. Structures 
resting upon these bottom lands were severely 
shaken, though in general there was little if any 
differential movement of the ground in such cities 
as Santa Rosa and San Jose. Structures located 
nearer the foothills of these same valleys, resting 
on firmer ground, were observed to suffer very 
much less. 

Within the confines of the city of San Francisco 
one finds evidence of great variation in shock 
closely related to and to be explained by the 
nature of the surface topography. It is a general ob- 
servation that the earthquake waves transmitted 
by the softer and less coherent materials and 
formations appeared to be much more destructive 
than waves which traversed the hard and more 
elastic rocks and other sound deposits. The bil- 
low-like effects that appeared in the streets of San 
Francisco near the Ferry house are most excellent 
examples of deformations in soft, incoherent ma- 
terials. The sliding and rolling effects observed 
on some of the sand dunes and especially along 
the hillside at the northern end of Van Ness 
Avenue may be cited as allied phenomena. The 
great contortion of sandy deposits on the south 
bank of the Salinas River in the vicinity of Salinas 
and Spreckels is another good example. 

[98] 



Charles D e r I e t h , Jr. 

POSSIBILITY OF FUTURE EARTHQUAKES NEAR 
SAN FRANCISCO 

I believe that the crust of the earth acts like a 
more or less brittle skin on the surface of a plastic 
globe. I believe the interior of the globe 
to be potentially plastic despite its relatively 
high density, because of the great pressure 
to which the material is subjected due to 
the enormous loads of superincumbent ma- 
terials. The crust can not be self-supporting like 
a spherical shell nor locally as a segment of a 
spherical dome because of the large radius of cur- 
vature of the earth's surface and small depth of 
shell or arched ring. For the earth's crust to act 
as a self-supporting stable arch or dome would 
demand the existence of arch ring or dome stresses 
in the crustal rocks far in excess of the crushing 
strength of granite. Wherever the pressure from 
within against the crust is relieved, the crust must 
sink, and where for some reason the interior in- 
creases its pressure against the crust the land must 
rise. The earth's crust may be conceived to rest like 
a brittle slab upon an interior of a semi-plastic na- 
ture; whenever the conditions of pressure between 
the crust and the interior become disturbed, the 
crust must give and adjust itself to put the stresses 
in the rocks into equilibrium. To produce this 
equilibrium the crust must give at its weakest 

[99] 



*? h e California Earthquake of i g o 6 

point. In this way a crack or slit, or as it is termed 
in geology, a fault, is produced. Within the con- 
fines of California one finds a region of structural 
weakness, and as has already been pointed out, the 
State is marked by a number of long fault lines 
running along the foothills of the high mountain 
ranges in the Sierra region and along the structural 
valleys of the coast ranges. Slippings and adjust- 
ments of the crust have occurred along these fault 
lines many times in the remote past, and the pres- 
ent evidences of geological faults and rifts are the 
accumulations of many past earthquake breaks. 
When a slipping has once occurred along one of 
these pronounced lines of weakness, either due to 
an actual rupture of the rocks or to the sundering 
of an old break, it is fair to presume that the crust 
in that vicinity has been set at equilibrium. It is 
also to be expected that a number of very minor 
shocks should follow in quick succession after a 
heavy earthquake. They represent secondary slip- 
pings and local readjustments after the main 
movement. A long period of time must then elapse 
before a sufficient accumulation of stress can result 
in the same region to produce another rupture and 
renewal of movement by overcoming the friction 
and partial cohesion of an old break. It is probable 
therefore that a heavy earthquake in the region of 
the main coast range fault will not occur in the 

[ ioo ] 



Charles D e r I e t h , Jr. 

immediate future, and that the crust in the region 
of San Francisco has been put into equilibrium for a 
considerable period of time. I believe it probable 
that Western California will not be subject to a 
heavy earthquake for at least a century, but earth- 
quakes can not be predicted and another one might 
come tomorrow. A shock of considerable seventy 
might occur at any time, and it is plain that think- 
ing men must be ready to expect surface dis- 
turbances somewhere in California in the next 
generation. 

It is our duty to anticipate these disturbances. 
Any one who has carefully studied earthquake 
destruction can not fail to appreciate that great 
structural losses are due primarily, except in the 
immediate region of a fault line or upon loose de- 
posits, to faulty design, poor workmanship, and 
bad materials ; let us hope through ignorance and a 
blind disregard for earthquake possibilities; yet I 
regret to add that I feel convinced that much of 
the bad work is due to a combination of criminal 
carelessness, vicious and cheap construction. 
Rather than try to tell outsiders that San Fran- 
cisco was visited by a conflagration I believe that 
it will do San Francisco and California in general 
more lasting good to admit that there was an 
earthquake, and that with honest and intelligent 
construction and the avoidance of geologically 

[IOI] 



T* h e California Earthquake of i g o 6 

weak locations for important structures, our losses 
within the earthquake belt would not have been 
so great. 

DESTRUCTIVE PATH OF THE FAULT LINE 

Referring again to Fig. 2, we note that the 
rift disappears in the ocean at the extreme north 
a few miles above Point Arena at the mouth of 
Adler Creek. From Adler Creek the fault may 
be followed southward approximately parallel to 
the coast line to Fort Ross, where it runs into the 
ocean about 2]/ 2 miles south of the fort. Earth- 
quake vibrations were very severe in the neigh- 
borhood of Fort Ross, I believe more severe than 
in the vicinity of San Francisco, but there were 
no important human structures to demolish. Fig. 
3 shows a redwood tree about six feet in diameter 
which happened to stand right on the fault line 
near Fort Ross. It was split into halves for 
a distance of 35 feet upward from the ground. The 
westerly half was sheared toward the north and 
actually moved past the east half a distance of 
about 8 inches. Fig. 4 shows a pine tree which was 
situated a few feet to the east of the fault line. 
It was thrown so that it leans toward the east. 
It was somewhat cracked at the base and its roots 
on the west side were torn, due to the shearing 
action along the fault line. The tree was 
subjected to torsion because it had roots on both 

[ 102] 




Fig. 3 — Redwood Tree, Situated on tin 
Sonoma County, California. 



Fault Line, near Fort Ross, 



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sides of the fault, which explains the crack- 
ing at the base of its trunk. Many trees 
were more or less ruptured along the fault where 
the line traverses timber growths; and in one 
place I observed leaning redwood trees for a con- 




Fig. 4 — Pine Tree Standing on the Line of Fault near Fort Ross, 
Sonoma County; the Ruptured Surface Shows the Character- 
istic Appearance of Newly Plowed Ground. 



siderable distance distinctly marking the passage 
of the fault through a forest. Leaning trees make 
a very uncommon and inspiring sight in a redwood 
growth, where the trees are over 200 feet in 
height. At Fort Ross, near the fault, I noticed 
many partly decayed trees and trees weak in parts 
demolished and snapped off by the shock, when 

[105] 



tf h e California Earthquake of i g o 6 

sound ones close at hand were undisturbed. I 
could not help thinking how Nature in this way 
pointed out her weak and her strong construction. 
In the cities that I have visited within the earth- 
quake belt, from Santa Rosa to San Jose, one can 
pick out the black from the white sheep in build- 
ings. Natural and human works behave alike. 
They are governed by the same mechanical prin- 
ciples. 

The fault line is lost in the ocean for some miles 
south of Fort Ross. It is again noticed as one 
proceeds southward, where it crosses the sandy 
spit of Bodega Head, which extends into the ocean. 
At this point the surface effects are very indistinct 
and of little moment to the engineer. 

Again, the fault line disappears in our south- 
ward journey, but it distinctly follows through the 
structural trough which forms Tomales Bay and 
appears on land again at the southerly end of that 
bay near Point Reyes and Olema. From Point 
Reyes to Bolinas Lagoon the fault line is extremely 
distinct and this region offers to the geologist and 
engineer equally interesting evidence. At Bolinas 
the fault disappears into the ocean outside of 
Golden Gate and does not appear on land again un- 
til we reach Mussel Rock on the San Francisco 
peninsula. Along the coast above Mussel Rock 
to Lake Merced great coastal disturbances were 

[106] 



Charles D e r I e t k , Jr. 

produced, due to landslides on the steep banks 
caused by the nearness of the shore line to the 
fault. Heavy landslides along the coast occurred 
also to the south of Mussel Rock at San Pedro 
Point and Devil's Slide, where the preliminary 
grading for the Ocean Shore Road, which is to con- 
nect San Francisco and Santa Cruz, was entirely 
wrecked. 

From Mussel Rock the fault proceeds south- 
ward along a chain of small lakes between the San 
Bruno marsh on the east and the coast ranges on 
the west. These lakes are numerous, and the ob- 
serving eye at once notices a connection between 
them and the characteristic geological formation 
which marks the line of the fault. Small basins or 
ponds, some brackish, some even salt, are of 
frequent occurrence along the fault line from Fort 
Ross to Hollister. Continuing southward from 
Mussel Rock and the chain of small lakes, the fault 
runs through a long and narrow structural valley, 
passes along the east bank of San Andreas Lake, 
follows the valley below that lake, and coincides 
with the longer diameter of Crystal Springs 
reservoir. 

It then continues southward somewhat to the 
west of Redwood City and Palo Alto (seven miles 
distant) and crosses the Narrow Gauge Railroad in 
the neighborhood of Wrights and Los Gatos. Here 

[ 107 ] 



T* h e California 'Earthquake of i g o 6 

mountain tunnels on the railroad have been made 
impassable by slides so that trains can not cross 
through the Santa Cruz Mountains from San Jose 
to Santa Cruz. Agnews and San Jose are twelve 
and thirteen miles respectively to the east of the 
rift. 

The fault may then be clearly followed to the 
region of Chittenden Station on the Southern Pa- 
cific Railroad, where it crosses the Pajaro River 
about 1,500 feet south of the station and passes 
right through the Pajaro River Railroad bridge. 
The fault line then proceeds inward to San Juan 
Bautista, or farther, where it leaves the region of 
important structures. 

DIFFERENTIAL HORIZONTAL DISPLACEMENT 

From Point Arena to San Juan all evidence 
clearly indicates that the ground on the west of 
the fault moved north from seven to nine feet rela- 
tively to the ground on the east. Straight fences 
that crossed the rift were invariably sheared so that 
they are out of alignment or offset from six to fif- 
teen feet. All things that crossed the fault (water 
pipes, houses, dams, and water courses) were 
sheared. It is clear to the observer that the ground 
on the west of the fault moved; that on the east 
did so too. Probably the material along the fault 
moved in opposite directions on the two sides, with 

[108] 




Fig. 5 — Fence near Fort Ross, Sonoma County, California, Offset 
Nine Feet at the Line of Fault. 



Charles D e r I e t h , Jr. 

the resulting displacements mentioned. The tear- 
ing- of the surface along the fault also clearly shows 
that there was some torsion in a clockwise direction 
when the eye looks downward. Fig. 5 shows a 
fence one-half mile south of Fort Ross which did 
not collapse, but was curved and bent to suit the 
lateral movements of the earth, so that its unmoved 
parts are now nine feet out of alignment. A second 
fence one-half mile farther south completely col- 
lapsed for a few feet on each side of the fault and 
was offset fifteen feet six inches. Near the head 
of San Andreas Lake a fence, Fig. 6, was offset 
seven feet. A roadway in the Point Reyes locality 
was dislocated about twenty feet. In all cases the 
west side moved north. 

The amount of offset along the fault at the sur- 
face is affected by the nature of the surface ma- 
terial. On marshy and on sandy ground and on 
steep hill slopes and alluvial valley lands, the offset 
is sometimes more and sometimes less than the 
average, due to secondary motions of the looser 
surface materials or to local landslides on the steep 
hillsides. It would seem that there was somewhat 
more, perhaps two feet, sliding motion along the 
fault line at its northern end near Fort Ross than at 
its southerly end near Pajaro, where the movement 
diminishes. 

[in] 



I 



T? h e California Earthquake of i g o 6 



DIFFERENTIAL VERTICAL DISPLACEMENT 

The relative horizontal movements along the 
fault were much more marked than the differential 




Fig. 6 — Fence near the North End of San Andreas Reservoir, San 
Francisco Peninsula, Offset Seven Feet at the Line of Fault. 



vertical displacements, although the old scarps now 
somewhat rounded by the weather show consider- 
able vertical differential motion for past times. In 
the north, in Sonoma County, due to the present 

[112] 



Charles D e ' r I e t h , J 



r . 



earthquake, one observes near Fort Ross a general 
lifting of the surface to the west of the fault line. 
The movement does not exceed four feet. In the 
south there is little, if any, differential vertical dis- 
placement. 

ABSOLUTE MOVEMENT OF THE CRUST 

Throughout the disturbed belt there is no doubt 
that the crust has been profoundly shaken. Lati- 
tudes and longitudes have doubtless been shifted 
a few feet, but it would be difficult to substantiate 
fully this statement. There is equally little evidence 
of change in elevation; yet mountain tops have 
probably been moved in elevation by small 
amounts. Only careful surveying and leveling and 
a comparison to geodetic records can throw light 
upon this question. The triangulation of the San 
Francisco Bay region is now being checked for this 
purpose by engineers of the United States Geodetic 
Survey. 

SANTA ROSA 

Santa Rosa, about fifty-two miles north of San 
Francisco on the California and Northwestern 
Railway, is nearly twenty miles east of the fault 
line. Nevertheless it was visited by great earth- 
quake and fire destruction. Eastern people have 
heard little of the losses of Santa Rosa because they 

[113] 



tf h e California Earthquake of i g o 6 

were overshadowed by the largeness of the destruc- 
tion at San Francisco; yet in my judgment, propor- 
tionately speaking, Santa Rosa's loss was greater 
than that of San Francisco. The city stands on al- 
luvial ground. Its business center was wiped out 
by fire and practically every brick building in the 
business district collapsed in the earthquake. I 
believe all but two or three of Santa Rosa's brick 
buildings were razed with the ground by the tem- 
blor. But it is my judgment that the shock was less 
serious in the northern city than in San Francisco. 
How then should the general destruction be ex- 
plained? The brick buildings of Santa Rosa were 
carelessly constructed. Lime mortar was almost 
invariably used with bad brick bond. The sand 
of the lime mortar used was what is locally known 
as "drift" sand, containing, according to a local 
engineer, practically fifty per cent of loam. When 
we remember that it has been too common a custom 
in California to lay brick for small structures with- 
out sufficiently wetting them, in fact almost dry, 
what else should be expected, especially when we 
further observe a most inadequate anchoring of 
the floor and roof frames to the outer walls, and a 
usual absence of necessary cross walls or frames. 
Besides brick buildings are not capable of with- 
standing heavy earthquake vibration. It is a fault 
of design more than of workmanship. Upon this 

[114] 




Fig. 7 — Santa Rosa Flour Mill. A Typical Brick Structure with 
Wooden Interior, Three Stories in Height; the Major Portion 
Completely Collapsed. 




Fig. 8; — Carnegie Library, Santa Rosa. A Typical Brick Building 
with Wooden Interior Framing; the Outer Walls Faced with 
Cut Stone. Buildings of This Type of Construction Invariably 
Were Shattered near the Roof Lines. The Picture Is Represen- 
tative of the^ Behavior of Stone-faced Buildings with Inadequate 
Wood Framing. 



C h 



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point I will speak more in detail later in reference to 
brick structures in the city of San Francisco. 

Wooden buildings in Santa Rosa with few excep- 
tions were unaffected by the earthquake except for 




Fig. 9 — A Scene in Santa Rosa Photographed Shortly after the 
Earthquake and Fire. The View Shows the Corner of Fourth 
and Mendocino Streets. The Ruins of the Court-House face 
Mendocino Street. On the Left in the Picture Is Seen the 
Collapsed Keegan-Brush Building, a Two-Story Brick and Stone 
Structure, Devoted to General Store Purposes. This Building 
Did Not Burn, and Ninety Per Cent of the Stock Was Saved. 
On the Right Side of Mendocino Street the Fire Destroyed 
Everything. In This Respect the Picture Is Instructive in That 
It Shows the Difference in the Destruction by Earthquake and 
Fire. 



the general throwing down of chimneys. The few 
frame houses which were wrecked collapsed be- 
cause of rotten or faulty and improperly braced 
underpinning to the first floor or cellar. Frame 



[117] 



*? k e California "Earthquake of i g o 6 

houses, well built, are adequate for earthquake 
countries. 

No railway or highway bridges in the vicinity 

of Santa Rosa suffered. No breaks occurred in 




Fig. io — The Collapsed Court-House Dome, Santa Rosa. The View 
Is Taken with the Camera on the Second-Story Roof; See Fig. 
o. The Court-House Consisted of Three Stories of Brick, the 
Third Story Smaller in Plan Than the Other Two. The Third 
Story Supported the Wooden Dome. 



the water works system, its artesian sources of 
supply, or its pumps. A few house-service pipes 
broke at the house lines. No sewers were crippled. 
It is plain to me that there was little or no unequal 
resultant movement of the ground at Santa Rosa 
such as one finds at the fault line. The destruction 
was due merely to earth vibration and the brick 

r 1181 



Charles D e r I e t h , Jr. 

buildings almost without exception collapsed like 
so many sand piles. 

The business portion of Santa Rosa burned be- 
cause fires started simultaneously in the rubbish 
and the facilities for fighting fire were too limited 
to cope with a conflagration. There was never a 
lack of water, in fact there was more water than 
under normal conditions, because the people were 
not using their natural supply; and for the same 
reason the pressure in the mains was greater than 
under normal conditions, although some local 
Santa Rosans ascribed the higher pressure to the 
effect of the earthquake on the subterranean 
grounds surrounding the artesian wells. 

Figures 7, 8, 9 and 10 show typical views of earth- 
quake and fire destruction in Santa Rosa. 

SAN FRANCISCO 

To the student of structures San Francisco in 
the month following the earthquake offered a field 
of observation so large that I hardly know 
where to begin to describe my impressions. 
Within the city limits one found most varied ex- 
amples of surface and foundation materials, from 
hard rock upon the hillsides to treacherous, filled 
ground along the water front of the bay and upon 
the old stream beds of the Mission Creek. Every 
degree of construction in building was presented, 

[119] 



°f h e California Earthquake of i g o 6 

from the first class steel cage constructed build- 
ings, locally called "Class A," to the cheapest types 
of brick and frame houses. All grades of work- 
manship, good and bad; all types of design, scien- 
tific and unintelligent; all degrees of construction, 
from honest to dishonest examples, were to be 
seen on every hand. On adjoining lots one found 
the so-called fire-proof structure and miserable fire 
traps huddled together. Or one saw the ruins of a 
building carefully fire-proofed within, but entirely 
lacking in exterior protection to resist a conflagra- 
tion from without. Many of the Class B struc- 
tures were clothed with iron shutters and gave 
some evidence that the designer and builder had 
at least thought of exterior fire-proofing; but with- 
in, the building was ready to burn like the contents 
of a furnace. 

Then as one walked through the desolate fire- 
stricken streets, one was constantly forced to com- 
pare the ruins of municipal and private buildings. 
Government buildings in general were well built, 
and it is not intended that they should be included 
in this criticism. There evidently was a difference 
in the construction of city buildings and those 
erected by private parties. Certainly there was a 
difference in their earthquake and fire resisting 
powers. School buildings and churches too, too 
often exhibited pronounced weakness in construc- 

[ 120] 



Charles D e r I e t h , Jr. 

tion. I believe these statements do not apply to 
San Francisco only. The attitude toward careless 
construction for buildings of community interest 
is entirely too prevalent throughout the United 
States. The facts have not been brought home in 
other large cities simply because those cities have 
not been so sorely tested as San Francisco was in 
April, 1906. It is perhaps right to say in this 
connection that it is unnecessary to consider the 
personal integrity of builders, or to insinuate criti- 
cism concerning the ability of the architect. What 
should be emphasized first and foremost is a gen- 
eral principle applicable to cities and communities 
all over the United States, namely, — that the public 
in the building of municipal structures, school 
houses and churches, expects far too much for the 
money appropriated. The result therefore is a 
hjuilding of improper construction, and we need not 
wonder that such buildings showed themselves 
seriously weak when tested by a severe earthquake, 
and helpless in a conflagration. 

The discussion for San Francisco naturally di- 
vides into three main parts: — (1), earthquake ef- 
fect upon structures; (2), fire-proofing of build- 
ings, and fire-resisting qualities of materials; (3), a 
critical digest to determine the best materials to be 
used and the most favorable types of design to be 
-employed to resist earthquake stresses and retard 

[121] 



tf h e California Earthquake of i g o 6 

the progress of fire. In this paper I will restrict my 
remarks almost entirely to the earthquake effects. 

EARTHQUAKE EFFECTS IN SAN FRANCISCO 

As pointed out earlier in this paper, the intensity 
of shock was not found to be constant over any 
given area, but was greatly affected by the nature 
of the ground surface. Structures resting on the 
rocky hill slopes of San Francisco suffered least. 
In the swales between the hills, upon comparatively 
firm ground deposited there slowly by natural 
processes, one found increased destruction. The 
shock was felt with still greater violence upon the 
sand dunes, while the worst destruction in the city 
was meted out on the artificially made lands near 
the water front and upon the old swamps. Roughly 
speaking, then, one may emphasize four varieties 
of ground: — (1), rocky hill slopes; (2), valleys be- 
tween the spurs of the hills; (3), sand dunes; and 
(4), filled ground; upon which, in the order named, 
was found earthquake destruction of increasing 
severity. 

But this classification can only be helpful for a 
preliminary and superficial discussion. Well-built 
structures on proper, deep foundations stood the 
shock on soft ground, while buildings of faulty de- 
sign went to pieces on much more favorable loca- 
tions. One may be easily led into error in judging 

[ 122] 



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D e r I e t k , 



J 



of the degree of shock by the amount of destruction. 
A complete knowledge of the type of structure, 
grade of workmanship, and properties of materials 
used, together with the geological considerations, 
is necessary to establish an intelligent conclusion. 




Fig. ii — Street Surface ui Front of the Ferry Tower, Showing 
Undulations and Cracks in the Asphalt Pavement. 



STREET AND SURFACE DEFORMATIONS 

Great distortion of the surface was best observed 
in the streets, and was found on the filled areas and 
in some places, on the sand dunes. The best local- 
ities for observation were: — (1), Market Street near 
the Ferry Building, Fig. 11; (2), the water front 
on both sides of the Ferry Building, Fig. 12; (3), 

[ 123] 



c f h e California Earthquake of i g o 6 

the corner of Howard and Spear Streets, where the 
J. A. Folger Company's building was saved from 
fire; (4), the corner of Mission and Seventh Streets, 
the location of the General Postoffice; (5), Van Ness 
Avenue at Eddy Street; (6), the north end of Van 
Ness Avenue and the streets on the hillside slope 
in that vicinity downward to the water front on the 
north; (7), Howard Street, between 17th and 18th 
Streets, Fig. 13; (8), Valencia Street, between 18th 
and 19th Streets, where the Valencia Hotel was 
wrecked with great loss of life, and the main water 
pipes were sheared; (9), Fourteenth Street, between 
Mission and Howard Streets; and, (10), the water 
front near the Potrero District. I might enlarge 
this list, but these are the typical examples. Ex- 
amples 5 and 6 represent surface distortions on 
sand dunes. The rest are examples of filled ground 
deformations. Upon the filled ground the surface 
was very generally thrown into billow-like waves, 
a type of disturbance which was best seen near the 
Ferry house. Upon the sand dunes the surface was 
shifted by sliding motion so that cracks and 
fissures appeared upon the streets at right angles 
to the direction of sliding. 

It was in these areas that the sewers and water 
pipes of the gridiron system were so generally 
crushed and broken. Even had the main conduits 
survived, water could not have reached the hy- 

[ 124] 



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drants in the lower Mission District. The brick 
sewers were uniformly helpless to resist destruction 
in these regions and the cast iron water and 
gas pipes fared no better. I believe reinforced 
concrete sewers in these districts would have shown 




Fig. 12 — Rupture of Car Tracks and Pavement on East Street, 
Corner of Pacific Street. 



much greater resisting qualities, but I am con- 
vinced that even such material could not with- 
stand earthquake stresses on the dividing line be- 
tween made and filled ground. At such points 
flexible joints might have helped the sewer and 
water pipes, but it is difficult to conceive of a prac- 
tical means for procuring flexibility at any given 

[125] 



tf h e California Earthquake of i g o 6 






point in a brick or concrete sewer. Moreover, it 
would be requiring a power of prediction not rest- 
ing in human beings to determine the proper loca- 
tions for flexibility. Important water pipes wher- 
ever possible should avoid soft ground by going 



■.....,. 


'■ 




1 

- 


$Mf*'.x : i';~* 






. 










"'"-"^HPWfflj 




ff^v^^ WC* 



Fig. 13 — Scene Corner of Howard and Seventeenth Streets Show- 
ing Rupture of Car Tracks, Sewer, Water and Gas Pipes. 



around it, and those that must traverse filled areas 
should be of riveted steel or wrought iron with 
flexible joints at intervals. Greater probability of 
resistance to rupture might be further insured by 
encasing pipes traversing the most treacherous 
ground in tunnels of reinforced concrete with suit- 
able clearance between the pipe and the tunnel 

[126] 



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walls. An added advantage of this scheme would 
be ready means of inspection. 

In discussing earthquake effects upon sewers 
and water pipes in the filled ground regions, one 
of necessity is led to consider fire problems as well 




Fig. 14 — Collapsed Frame Houses on Howard Street, between 17th 
and 18th Streets. The One on the Left Is Completely Rased. 
At This Place the Earth Movements Were Especially Severe, 
and Even Good Construction Would Have Suffered. 

because the water supply and fire questions are so 
vitally related. Water mains should be generously 
provided with a system of cutoff valves command- 
ing the direction of flow through the pipes of any 
given locality. At the time of the earthquake San 
Francisco was in dire need of a salt-water system, 
and immediate steps should be taken to provide 

[127] 



The California Earthquake of i g o 6 

such a system and to secure a number of powerful 
fire boats. 

ORDINARY FRAME HOUSES 

Many frame buildings collapsed on the filled 
ground, Fig. 14; and an unreasonably large num- 
ber on the more substantial areas of the city. Some 
of the destruction in the made land district was 
unavoidable, but much of the general collapse of 
frame houses was due to improper underpinning 
in the foundations. Such houses virtually stood on 
stilts; consult Figs. 15 and 16. Moreover, the 
cheaper frame buildings were provided with care- 
lessly constructed brick chimneys built with weak 
lime mortar; naturally the brick work cracked to 
pieces. It is therefore easy to see why so many 
of these houses burst into flames immediately after 
the earthquake. It is said that fifty-seven fire 
alarms were sent to the Fire Department within 
the first half hour. Of course not all of these fires 
were produced by fallen or cracked chimneys in 
frame buildings. Some were similarly started in 
cheap brick structures, which are just as readily in- 
flammable, — and still others by the breaking of 
electric wires of high tension, or through improper 
electric insulation of power wires. 

Carefully built wooden-framed houses are 
especially well adapted to withstand earthquake 

[128] 




Fig. 15 — Frame House Wrecked in Santa Rosa, 
Decayed Underpinning. 



Due to Weak and 




Fig. 16 — Collapsed Frame House in San Jose Showing the Effect 
of a Lack of Transz'erse Framing and an Absence of Continuity 
in the Vertical Sticks at the Floor Levels. 



Charles D e r I e t h , J 



r . 



shock and represent a most desirable type for small 
dwellings. The weak feature is the brick chimney. 
But even this can be built so that cracking will not 
be so complete as to cause fire. For earthquake 
countries wooden buildings should be intelligently 
framed to act like an elastic cage or unit, and the 
foundations should be carried below the surface 
sufficiently to reach firm ground. It is too common 
a practice which completes one story of a framed 
house before starting the frame for the next story. 
Where there is no continuity in the main wall fram- 
ing from floor to floor, weakness exists at the floor 
level; consult Fig. 16. 

If brick chimneys must be used it is a mistake 
to use strong mortar above the roof line. With 
strong mortar a chimney top will fall in one piece 
and crash through the roof; with weak mortar it 
will disintegrate and the individual brick will roll 
off the roof. 

ORDINARY BRICK BUILDINGS 

The most general destruction by earthquake in 
San Francisco was observed in ordinary brick 
buildings. Brick walls were usually thin, of 
careless bond, and built with lime mortar of little 
strength. Apparently many brick walls were laid 
without wetting the brick before applying the mor- 
tar, because one found so many cases where the 

[131] 






*f h e California Earthquake of i g o 6 

crumpled piles of brick showed clean surfaces, the 
mortar not having adhered to the brick to any de- 
gree. These buildings were of timber framing 
within, and the floors and roofs were improperly 
anchored to the outer walls. The earthquake shook 
out whole sides of brick buildings because there 
was no provision for a proper tying or anchoring 
of the walls from within. The so-called "fire walls" 
above the main cornice were thrown down in al- 
most every case. Had the earthquake occurred 
later in the day, the falling of brick from fire walls 
would have caused many deaths. 

Where buildings of this class had trussed roofs 
of timber, the framing was generally imperfect. 
These roofs commonly rested on inclined rafters 
with no bottom cross tie to keep the rafters from 
spreading. The earthquake vibration tended to 
drop the peak of the roof and spread the ends, 
which, in kicking against the walls, forced them 
out and threw them down. In this way a number of 
brick school houses were severely shattered. Many 
brick buildings were built like weak boxes, with no 
adequate provision for transverse stiffness, because 
the structures entirely lacked transverse brick 
walls or frames. Brick structures in San Francisco 
and vicinity should never be built with lean lime 
mortar. One part of cement to four or five of lime 
mortar would give very much better results. At 

[ 132] 



Charles D e r I e t h , Jr. 

least every other joist of the floor system ought 
to be carefully tied to the outer brick walls. The 
roof similarly should be anchored to the walls ; and 
its main trusses should have properly designed 
lower chord tie rods, and not depend for their re- 
sistance to spreading upon the stiffness of the side 
walls of the building. Foundations of these struc- 
tures should also be made with great care to have 
them act as units to prevent unequal settlement. 

The prime requisite for a structure to withstand 
earthquake shock is elasticity; that is, the ability 
to return without serious damage to its original 
shape and position after being distorted. It should 
vibrate without offering great resistance to distor- 
tion; in other words, it should yield readily. The 
wooden framed and the steel framed building an- 
swer this requirement. To an almost equal extent 
the reinforced concrete building does so also. But 
structures of brick and stone built of blocks, like 
brick work and cut-stone masonry, with horizontal 
and vertical mortar joints do not answer the 
requirements of yielding and elasticity to any desir- 
able degree. This is especially true when the in- 
terior framing is of wood and of the weak and 
faulty design depicted in the preceding paragraphs. 
Brick and stone walls when not sufficiently rein- 
forced and intelligently strengthened and sup- 
ported by steel framing are inadequate for import- 

[i33] 



'The C a I i f o r 



n i a 



Earthquake of 1906 



ant buildings in an earthquake country. Consult 
Fig. 17. 

While I have been decidedly severe in condemn- 
ing block-work construction I must admit that 
some brick structures made a good showing. They 




Fig. 17 — A San Jose High School. 
with Wooden Interior. 



Ordinary Brick Construction 



are the exceptions that prove the rule. For every 
brick building that withstood the shock, it is easy 
to give a number of examples of complete failure. 
St. Patrick's Seminary, at Menlo Park, is an 
example of most excellent brick work, yet it was 
decidedly shattered in the main towers. It is not 
unreasonable to say that where brick structures 
withstood the shock they did so in spite of the fact 

[i34] 



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that they were built of blocks or because the shock 
was slight or the building favorably situated. 

In San Francisco there were a number of large 
brick structures of most excellent type which 
weathered the earthquake with practically no 




Fig. 18 — St. Francis Church, San Francisco; an Example of Ex- 
cellent Brickwork. 

damage. I refer to several churches, see Fig. 18, to 
the Custom House or Appraiser's Building and to 
the Palace Hotel. The walls of the Appraiser's 
Building were thirty-six inches thick. The Palace 
Hotel was built immediately after the earthquake 
of 1868 and was intended to be earthquake-proof. 
The outer walls were most carefully designed, the 
window openings were crowned with arches and 

[i35] 






tf h e California Earthquake of i § o 6 

the interior of the building was divided into com- 
partments by numerous cross walls running paral- 
lel to both sides of the building. Looking down 
upon the ruins of the structure one saw a honey- 
comb of brick walls giving lateral stiffness in all 









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Fig. 19 — Fir j* Baptist Church, Oakland, California. The Dangerous 
Tower Was Pulled Down Several Days after the Earthquake. 

directions. Iron rods were embedded in the walls. 
The old Palace Hotel therefore should not be 
classed as a simple brick building, for it contained 
some attempt at reinforcement. 

STONE STRUCTURES 

Heavy stone structures, without steel frames, 
especially where the outer walls were not properly 

[136] 



Charles D e r I e t h , Jr. 

tied to the interior floor and roof frames, suffered 
severely throughout the earthquake belt; see Fig. 
.8. Too many structures of this type for architect- 
ural reasons are made top heavy; see Fig. 19. 
Much of the recent construction at Stanford Uni- 
versity may be criticized along these lines. In Oak- 
land, Berkeley and San Francisco, heavy masonry 
church towers were invariably demolished, except 
where they were properly reinforced by interior 
steel frames or were strengthened by interior cross 
walls and tying rods. Heavy stone ornamentation 
should be discouraged and heavy stone cornices 
should be avoided. Where architectural effect is 
insisted upon, no expense should be spared in 
anchoring heavy stone cornices by the use of metal. 

CHIMNEYS 

Chimneys in San Francisco were built of brick 
and very often without cement in the mortar. With 
few exceptions the chimneys were thrown down by 
rupture within the middle third of the height. A 
number of lives were lost by falling power house 
chimneys; see Fig. 20. In the future I believe 
chimneys should be built of reinforced concrete and 
not of brick. Where brick is insisted upon, the bond 
should be carefully provided for, the mortar should 
be rich in cement and there should be some metal 
reinforcement. 

[i37] 



<? h e California Earthquake of i g o 6 



CLASS B BUILDINGS 

There is little to say regarding the earthquake 
effect upon the so-called "Class B" buildings. These 




Fig. 20 — Fire Ruins of a Power-House of the San Francisco Gas 
and Electric Company, Station C. The Chimney of This Struct- 
ure Fell During the Earthquake Shock, Demolished a Part of 
the Equipment and Killed One Person. 

structures consisted of self-supporting walls with 
an interior framing, partly of metal and partly of 
wood, with cast iron columns too often in evidence. 
For large structures of considerable height, one 

[138] 



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certainly should not advocate self-supporting walls 
for earthquake countries. The Mills Building in 
San Francisco, Fig. 21, anoTherwise excellent 
structure of ten stories, was designed with self-sup- 




Fig. 21 — The Mills Building, San Francisco ; Self-Supporting Brick 
Walls, Interior Framing of Steel, Floors and Partitions of 
Hollow Tile. 



porting walls and with main columns breaking 
joints at every floor level. After the earthquake 
the walls of this structure leaned from seven to nine 
inches into Bush Street. While the structure did 
not appear to be severely racked by the earthquake, 
the fact that the walls bore little relation to the in- 
terior frame, and the interior frame lacked con- 
tinuity of columns at every floor, would not lead 

[ i39] 



tf h e California Earthquake of i g o 6 

me to recommend such a type of structure for an 
earthquake country. Moreover, the type exhibits 
great weakness in resisting fire because the walls 
tend to leave the frame. In Class B buildings it 
was a general observation to note heavy cracks run- 



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R?l 


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11 » w 1 


- 1 « ( 




■ - 


« m M 1 

t ■' ■ f ■'; " 
m, if gS3s* ' r ! : 



Fig. 22 — Fire Ruins of the Cowell Building, a Class B Structure, 
Showing the Great Destruction by Fire. 



ning diagonally in the outer walls. Such X-shaped 
cracks are also found in the brick work of steel-cage 
constructed buildings, but they obviously produce 
much more serious consequences in the Class B 
building, which has no steel frame upon which to 
depend for unity and coherence. 



[ Ho 



Charles D e r I e t h , Jr. 

REINFORCED CONCRETE BUILDINGS 

There were no reinforced concrete buildings in 
San Francisco because before the fire there had al- 
ways been successful opposition to their introduc- 
tion. In a few buildings reinforced floors and col- 
umns had been used, but there were no outer walls 
of reinforced concrete. Reinforced floors were 
common in Class A structures, where they shared 
favor with hollow tile floors. The little San Fran- 
cisco evidence that one finds, considering also a 
few reinforced structures, or partially reinforced 
structures in other places, such as in Oakland and 
Palo Alto, leads one to the conclusion that build- 
ings scientifically designed in reinforced concrete 
present admirable qualifications for earthquake re- 
sistance. There is no reason why reinforced con- 
crete cage constructed buildings of at least six or 
eight stories in height should not be built in San 
Francisco. A reinforced concrete structure, when 
intelligently designed, generously proportioned 
and honestly built, is a monolith of great coherence 
and high elasticity, combining the very properties 
best able to resist earthquake vibration. 

CLASS A BUILDINGS 

Class A structures stood the earthquake shock 
admirably. Their steel frames were not materially 
impaired. These buildings vibrated like tuning 

[141] 



tf h e California Earthquake of i g o 6 

forks. It appears that the base of such a structure 
oscillated and moved with the earth, while the top 
tried to remain quiet. This statement is substan- 
tiated by the general evidence that less shock was 
felt in the upper stories of high buildings than in 
the floor levels near the street. Again it seems to 
be a fact that books and other loose objects were 
less disturbed and thrown down in offices in upper 
stories than in the those near the basement. The 
main steel columns of Class A buildings should be 
as continuous as possible from roof to cellar. Splices 
should be generously built, and it is always wise 
to run column pieces through several floors. These 
high structures were subjected to a considerable 
racking stress at floor levels, as is evidenced by the 
lines of rupture in brick walls at the floor horizons. 
In the future I believe that steel frames for Class 
A buildings should be provided with considerable 
knee-braced framing in the vertical planes between 
the main floor girders and columns to which they 
rivet; and wherever possible, diagonal framing 
should be introduced similar to that provided to re- 
sist wind stresses. Wind stresses very commonly 
are fictitious or imaginary, and certainly never ap- 
proach the limits provided for; but earthquake 
stresses, while they fortunately do not occur very 
often, are intense and of the nature of impact for- 
ces. The engineers upon whom may devolve the 

[142] 



Charles D e r I e t h , J 



r . 



design of Class A skeletons in the immediate future 
should insist upon their structural requirements 
with greater determination than in the past, and 
not allow the architect to injure the strength of 
the building for the purpose of securing some less 
necessary architectural feature or embellishment. 

Earthquake forces, relatively speaking, are un- 
limited in amount when the strength of human 
structures is under consideration. The amount of 
earthquake stress produced in a member of a struc- 
tural steel frame is directly proportional to the re- 
sistance offered. The stiffer a structure, the greater 
will be the induced stress produced by earthquake 
vibrations. The more a structure is capable of 
yielding, like a willow tree to the storm, the less 
will be the tendency for earthquake rupture or 
collapse. 

A committee of the American Society of Civil 
Engineers in its report on buildings states: "Suf- 
ficient evidence is at hand to warrant the statement 
that a building designed with a proper system of 
bracing to withstand wind at a pressure of thirty 
pounds per square foot will resist safely the stresses 
caused by a shock of an intensity equal to that of 
the recent earthquake." For bridges and towers, 
engineers usually provide diagonal members to re- 
sist wind stresses. They would use diagonal fram- 
ing in high buildings also, except for the objection 

[i43] 



The California Earthquake of i g o 6 

of the architect. It is my judgment that diagonal 
framing is not desirable for high buildings in earth- 
quake countries. Such framing consists of tri- 
angular parts. Geometry teaches us that a triangle 
can not change its shape without changing the 
lengths of its sides. Triangular framing therefore 
is stiff and unyielding and calls forth earthquake 
stress to the full capacity of the diagonal wind mem- 
bers. If a stiff frame of triangles is subject to 
earthquake vibration of severity, rupture at the 
weakest places is extremely likely. The effect of 
the earthquake on the Ferry tower in San Fran- 
cisco justifies the above statement. In this tower 
diagonal wind bracing was used. In the fifth and 
sixth floors of the towers the diagonal rods were 
either buckled or ruptured or broken at the eye- 
ends. In some cases the rivets connecting the 
gusset plates and angles sheared off, the stress 
finding in each case the weakest point. The 
stresses exceeded the equivalent of a thirty-pound 
wind pressure many times. This is proven by the 
permanent set or elongation of the diagonal rods. 
In five cases, including three two-inch square rods,, 
it was necessary to cut off the screw ends to take 
up the slack. The total stretch in some cases- 
amounted to more than three inches. 

For earthquake conditions triangular framing 
for high buildings is not so desirable as a rect- 

[ i44] 



Charles D e r I e t h , Jr. 

angular framing with stiff joints and continuous 
members. In steel buildings, rectangular framing 
is best produced by substantial continuity in the 
main columns and by bracing these columns with 
deep horizontal spandrel girders; or by more shal- 
low spandrel and floor girders strengthened with 
heavy knee braces. 

Unlike the triangle, the rectangle can change 
its form without changing the lengths of its sides, 
With spandrel girder and knee bracing, therefore, 
the main columns by their elasticity and continu- 
ity can yield and vibrate to a considerable extent 
without endangering the integrity of the building's 
frame. 

I therefore conclude that the best type of fram- 
ing in a steel skyscraper consists in the generous 
use of deep spandrel girders, preferably of the lat- 
ticed truss type. The new Humboldt Savings 
Bank on Market Street is an excellent example. 
The old Call Building has an excellent lateral 
framing. 

In the basement of the Flood Building, on the 
south side, a number of rivet heads were sheared 
off in the connections between the girder beams 
and column shelf angles upon which the beams 
rested. These ruptures were undoubtedly pro- 
duced by racking motion coincident with the earth- 
quake vibration. Racking stress in buildings 

[i45] 






The California Earthquake of i g o 6 

certainly had its greatest destructive tendency in 
the first floor above the ground. 

Earthquake vibration in high buildings puts a 
considerable stress upon the floor connections and 
columns, but does not tend to produce much des- 
tructive effect in the floors; on the other hand, it 
is clear to see that it does produce a very consider- 
able shearing stress upon partitions, tending to 
destroy and crack them. This observation leads 
me to state that I do not advocate hollow tile parti- 
tions for high buildings in earthquake localities. 
Reinforced concrete partitions are much more suit- 
able. Double metal lath and plaster partitions also 
have merit. I have no particular grievance against 
hollow tile construction, but partition tile is not a 
good earthquake material. It is essentially brittle, 
and difficult to build into a coherent mass. It can 
not stand flexure or distortion of any kind. For 
similar reasons I believe there is decidedly more 
merit in reinforced concrete floors than in hollow 
tile floors. 

The earthquake vibration very generally pro- 
duced X or so-called "earthquake cracks" in the 
outer curtain walls of Class A structures. It was 
very common to see brick work shattered between 
windows; and on large side walls, without window 
spaces, examination showed cracks running at 
angles of 45° to the horizon. Often heavy crack- 

[146] 



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ing was observed at a corner of a building, see 
Fig. 23. Such destruction is not so serious in 
Class A buildings as in those designated Class B, 




Fig. 23 — The Monadnock Building, Showing Heavy Diagonal Cracks 
in the Brick Curtain Walls along the Northeast Corner for the 
Full Height of the Structure. 



which have self-supporting walls, because it is a 
simple matter to restore the wall at any floor level 
of a Class A structure without disturbing the rest 
of the building. Much of the heavy cracking found 



i47 



tf h e California Earthquake of i g o 6 

in Class A buildings may, however, be attributed 
to improper bond or anchoring in brick work, and 
to mortar too lean in cement. To me a building 
with a properly designed steel skeleton and light 
walls of reinforced concrete, supported by the main 
frame at each floor level, represents a type contain- 
ing very much more merit to withstand earthquake 
shock than structures with brick and terra cotta 
curtain walls. Such reinforced concrete curtain 
walls can be made lighter than brick and terra cotta 
walls, thus reducing the dead weight of the struc- 
ture. Brick, stone, and terra cotta curtain walls 
can be safely used, however, especially when care- 
fully anchored to the structural frame. 

Exposed side walls of a number of Class A 
buildings had face brick finish on ordinary brick 
curtain walls to give a dressed appearance. In 
most of these cases the face brick were tied to the 
backing by no other means than what is commonly 
called the clipped course bond. The racking of 
the earthquake threw out large areas of such face 
brick. The best example that came to my notice 
was found on the west wall of the Merchants' Ex- 
change Building. The clipped course bond for 
facing brick should be prohibited. 

I have already stated that in high buildings the 
earthquake racking was most severe near the street 
level. One found in nearly every Class A building 

[148] 



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prominent cracks in the first story walls (Fig. 24), 
especially at points where heavy weights were con- 
centrated upon corner columns. The stone work 
of corner columns was severely cracked where the 
masonry rested upon concrete under the sidewalk, 





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ip^p*4jt 




pyfiiftii 




WC-- ' -iwfiiBilT" - 


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Fig. 24 — Flood Building, Northwest Corner, Showing Heavy Earth- 
quake Cracking of the Sandstone Masonry Enveloping the Steel 
Corner Column. 



but hardly at all where the stone masonry was car- 
ried by the steel frame. Main columns acted like 
stilts to support the superstructure above the ceil- 
ing of the street floor, and prevented the collapse 
of many a building by column rigidity and con- 
tinuity at the floor connections in the level of the 
second floor. It is plain that such floor connections 

[ 149] 



*? h e California Earthquake of i g o 6 

can not be too carefully designed. The most pro- 
nounced cracks at first-story columns were found 
in the Flood Building. One saw them also to good 
advantage on the sandstone front of the St. Francis 
Hotel (Fig. 25). Cracking of this character is not 
an evidence of weakness in the body of the building. 

In Class A structures terra cotta was very gen- 
erously and profusely used for ornamentation on 
the facing of the curtain walls of the street fronts. 
Being a material of the same nature as hollow tile, 
it is brittle and lacks toughness. It was generously 
spalled by earthquake vibration, and, while I by no 
means wish to imply that its use should be pro- 
hibited, I think it should be very carefully selected, 
be well burned, be used with greater thickness than 
in the past, and the hollows in the blocks should 
be filled. Highly ornamented terra cotta should 
be discouraged. The earthquake produced con- 
siderable spalling in the terra cotta of the Mills 
Building, and very generally damaged the terra 
cotta face of the Fairmont Hotel, especially on the 
north front (Fig. 26). 

The foundations of high Class A buildings with 
small bases can not be designed with too great 
care. Where such structures rest on sand or near 
the filled ground areas, the foundations should be 
deep. Deep pile foundations have given excellent 
results, even on the filled ground. It is a general 

[150] 



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observation that structures resting on pile founda- 
tions in the made ground were much less affected 
than adjoining buildings on shallow foundations. 
The cable roadway on Market Street, where it 
approaches the Ferry Building, was founded on 




Fig. 26 — Fairmont Hotel; North Front, Showing Earthquake Cracks 
in the Terra-Cotta Veneer of the Second Story Walls. 



piles, and it sank little when compared to the gen- 
eral dropping of the street surface along the sides 
of the tracks. Other types of foundations, such as 
that under the Call Building, which is of the solid 
slab variety, have given equally good results. 

Intelligently built foundations, not only for 
buildings but for all kinds of structures, were un- 

[i53] 



*? k e California Earthquake of i g o 6 

affected by the earthquake. Well-built founda- 
tions are adequate. Depth is a prime consideration. 
Important structures should not be built on 
treacherous ground. The site of the general Post- 
office (Fig. 27) was very unhappily chosen. That 




Fig. 27 — General Postoffice, Southwest Corner, Showing Severe 
Distortion and Subsidence of the Sidewalk and Street Levels. 



building, while exceedingly well built, rests on 
filled ground, and under its southwest end ran an 
arm of the Mission Creek. In this vicinity the 
ground was very much disturbed, and the street 
fell away from the building. The structure, while 
it stood and was saved from fire, was severely 
racked, and its beautiful granite fronts were badly 

[154] 



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cracked on all sides. The interior partitions of the 
building were of double hollow tile, and were 
greatly destroyed. The structure represents an 
example of a building with heavy masonry walls 
with a partial and too light a steel frame. Con- 




Fig. 28 — Earthquake Cracks on Sandstone Piers of the Ferry Build- 
ing. These Piers Enclose Steel Columns with a Complete Air 
Space between the Steel Columns and the Stone Blocks. This 
Explains the Large Amount of Cracking and Shows That the 
Stone Piers Are Not Required for the Support of the Second 
Story. 



sidering the material upon which it rests, the build- 
ing withstood the earthquake surprisingly well. 

The Ferry house exhibited another example of 
excellent construction in a treacherous location. 
Due to the movements of the filled ground, there 
was no doubt a considerable pressure brought to 

[i55] 



T* h e California Earthquake of i g o 6 

bear against the structure from the land side, tend- 
ing to thrust it into the bay. The building rests on 
piles in large clusters, and withstood its severe test 
admirably. The top of the south end wall fell out. 
The stone work near the street level on the main 
pilasters was badly cracked (Fig. 28). In the 
second story horizontal joints were opened 
throughout the west front length of the building. 
The marble plates on the interior walls were much 
broken. The tower was shaken like a tree or flag- 
pole in a vertical plane east and west, nearly co- 
incident with Market Street's length. The east 
and west faces of the tower were therefore badly 
racked, just above the roof of the main building, 
and the stone facing at these places was thrown 
down, causing considerable destruction in the in- 
terior in the central portion of the building below 
the tower, see Fig. 29. The upper portion of the 
tower was originally designed in stone, but the con- 
sulting engineers advised the substitution of metal 
sheeting to reduce the weight, and this fortunately 
was done. Had the upper portion of the tower 
been of stone, I believe the destruction would have 
been very much more serious. The stone facing of 
the tower was backed with brick, and this masonry 
was supported by a steel frame, as in Class A build- 
ings. It appears that the steel frame was built too 
light, especially the diagonal members. These 

[156] 



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diagonals should have been heavier, and of stiff 
sections instead of rods. Some of the diagonal 
rods were snapped and some gusset plate connec- 




Fig. 29 — The Ferry Tower Shortly after the Earthquake. 

tions and riveted joints were ruptured. I have 
already referred to the superior merit of quadri- 
lateral framing, using spandrel girders and knee 
bracing. The tower was rapidly dismantled, the 



i57 



'the California Earthquake of i g o 6 

steel frame strengthened and repaired and re- 
clothed with reinforced concrete curtain walls. 

THE FIRE DAMAGE IN SAN FRANCISCO 

The lessons to be learned from the San Francisco 
conflagration are many, though not new. A dis- 
cussion of this subject will in the main repeat the 
results of the studies of the Baltimore fire. Never- 
theless, the question of fireproofing in San Fran- 
cisco should and will receive the closest attention. 
It is a very large and important subject and of 
sufficient dignity to warrant a description by itself. 
Being without the purpose of this paper, it is not 
here treated. I will only add that such a discussion 
should pay some attention also to the fire calamities 
in Santa Rosa. 

EARTHQUAKE DESTRUCTION TO THE SAN FRANCISCO 
WATER WORKS 

The important destruction to the works of the 
Spring Valley Water Company occurred between 
San Mateo and the city of San Francisco. There 
was practically no damage to the water sources and 
works in Alameda County. 

The Alameda conduit between the source and 
Burlingame lies in a region of lesser disturbance, 
and appears to have been subject to about the same 
degree of shock as the Contra Costa Company's 
works, which supply water to Alameda, Oakland 

[158] 



Charles D e r I e t h , J r , 

and Berkeley. It is significant to observe that 
there seems to have been little or no damage to the 
submerged part of the Alameda conduit where it 
runs under and across the southern end of San 
Francisco Bay. 

The map, Fig. 30, clearly shows the water 
works property of the San Francisco Bay cities 
within the region of considerable earthquake dis- 
turbance. This map is taken from the Earthquake 
Reports of San Francisco members of the American 
Society of Civil Engineers^ consult the Proceedings 
of that Society for March, 1907. 

The Pilarcitos reservoir is to the west of the main 
fault line, and is separated therefrom by a range of 
hills known as the Sawyer Ridge. That reservoir 
is thoroughly intact, and its 95-foot earth dam is 
unaffected. The waste-way conduit connecting it 
with San Andreas Lake is also intact. 

The main fault line runs through Crystal Springs 
Lake, but in no way appears to have affected the 
imperviousness of its bottom. The older Crystal 
Springs dam, which separates that lake into halves 
is crossed by the fault. Evidence on the roadway 
and roadway fences over the dam shows that the 
dam was sheared about five or six feet in the man- 
ner already explained under the heading "Hori- 
zontal Differential Motions Along the Fault." This 
dam, like the San Andreas dam, aside from trans- 

[161] 



°r h e California Earthquake of i g o 6 

verse cracks parallel to the fault line, also exhibits 
a number of longitudinal cracks along the roadway. 
When the huge concrete dam was built at Crystal 
Springs, the older dam became submerged, and to 
produce the roadway a fill was placed upon the dam 
of less coherence than that of the material of the 
original dam. It is impossible to determine 
whether the imperviousness of this dam below its 
upper and newer portion has been affected by the 
shearing action because the water is at the same 
level on the two sides. From the behavior of the 
San Andreas dam, however, I am led to believe 
that the shearing, even of five feet, has not been 
sufficient to cause serious perviousness, and should 
the water be released from one side of the dam, I 
believe it would be retained on the other. If my 
argument is valid I believe it indicates one ad- 
vantage of a properly constructed earth dam with 
a clay core over a light dam of masonry and especi- 
ally a light arched masonry dam of bold design 
like the Bear Valley, in Southern California. 

The huge concrete dam at Crystal Springs, 115 
feet in height above the natural surface, is parallel 
in length to the fault line. Its curvature is slight 
compared to the dimensions of its cross section. 
Arch action is negligible. The dam should be con- 
sidered as a straight gravity dam. It was probably 
subjected to a series of thrusts and pulls in vertical 

[162] 



Charles Derleth. J 



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planes along its length since it parallels the fault. 
Its inner face has a much heavier batter than the 
Rankine or Wegmann calculations would require. 
The engineer of the dam, Mr. Hermann Schussler, 
states that he made the batter of the inner face 
one in four because of earthquake possibilities, he 
having experienced the earthquake of 1868. This 
dam is practically unaffected by the earthquake. 
Some who have examined it state that they have 
found slight cracks near the base of the down- 
stream toe, but I did not see them, and they cer- 
tainly are not serious. The intake works at this 
dam, the Crystal Springs Pumping Station, and all 
accessory construction in the neighborhood were 
left practically intact by the earthquake. 

The fault touches the eastern edge of San An- 
dreas dam, an excellent construction of earth and 
clay, 93 feet in height above the original surface of 
the ground. The fault line is nearly at right angles 
to the dam. As an eye witness I am convinced 
that this dam was subjected to a most severe earth- 
quake shock, and since it retains the waters of San 
Andreas Lake, just as well as before the earth- 
quake, it should be a source of great satisfaction 
to its designer and builder. Skilfully designed and 
well built earth dams have been proven by our great 
earthquake to be structures of great stability, de- 
serving of increased confidence. 

[163] 



tf h e California Earthquake of i g o 6 

At the San Andreas dam the ground on the east- 
ern bank was considerably scarred by cracks run- 
ning northwest, where the fault line crosses the 
nose of a hill which naturally projects to form the 
dam's abutment. There must have been some 
motion at this point, possibly five or six feet, but it 
is not clear on the surface. The cracks which were 
pronounced in this nose or abutment were in the 
abutment and not in the dam itself. There were 
a number of smaller cracks running in the same 
direction at the extreme westerly end of the dam. 
On the dam's roadway there were small longitudi- 
nal cracks to be observed throughout its length, 
apparently due to the unequal settling of the tri- 
angular masses with respect to the core, but they 
were not serious. I am convinced that an earth 
dam properly constructed will stand a violent shock. 
Wherever possible a dam should not cross a geolog- 
ical fault at right angles. 

The wooden flume starting near the Crystal 
Springs Pumping Station, which enters the San 
Andreas reservoir near the east end of its earth 
dam, completely collapsed just below that dam 
where the main fault line crosses the flume. At 
this place the flume was supported on a wooden 
trestle about fifty feet in height. In the same 
locality a waste-way conduit built by day labor, of 
selected brick with cement mortar, provided a dis- 

[164] 






Charles D e r I e t h , Jr. 

charge from San Andreas Lake into the valley be- 
low the dam to discharge water into Crystal 
Springs reservoir. The gate-house for this conduit 
is near the eastern end of San Andreas dam, about 
300 feet from the fault line. It is built of selected 
brick with cement mortar, and exhibits no cracks 
whatever. About 1,000 feet below the dam the 
brick conduit curves to the west to its discharge 
point, and in so doing crosses the fault line. At 
this crossing the conduit was sheared completely, 
but due to the excellence of the mortar, the brick 
was sheared more readily than the cementing ma- 
terial of the joints. This speaks volumes when we 
reflect upon the general destruction of brick struc- 
tures throughout the earthquake belt. 

The Crystal Springs conduit was not damaged 
between Crystal Springs dam and San Mateo, but 
between that city and San Francisco it was rup- 
tured in a number of places where it crosses the 
marshes. It is mainly a 44-inch laminated wrought 
iron pipe, % inch in thickness, with riveted joints 
and rivets J^ inch in diameter. The worst destruc- 
tion occurred in a distance of about 1,600 feet 
where the pipe crosses a salt marsh between San 
Bruno and South San Francisco. Here the pipe 
rested upon a wooden floor supported by pile bents. 
These piles on the average penetrated the mud to 
a depth of about 40 feet. The salt marsh evidently 

[165] 



T* h e California Earthquake of i g o 6 

shook like a bowl of jelly, the vibration being 
mainly in a south-southeasterly direction or nearly 
at right angles to the length of the trestle. It ap- 
pears that during the vibrations of the earthquake 




Fig. 31 — Rupture of the 44-inch Crystal Springs Conduit on the San 
Bruno Marsh; Picture Taken May 2, 1906. The Wooden Sup- 
ports under the Pipe Are Temporary Forms Built after the 
Catastrophe. The Pipe Has Been Straightened Preparatory to 
Repairing the Transverse Riveted Joints. 



the trestle moved with mother earth. The pipe, 
due to its inertia, tended to remain quiet. As a re- 
sult the pipe was alternately thrown from one side 
to the other of the trestle floor and its wooden box 
covering was generally smashed. The pipe broke 
at transverse circular riveted joints, sometimes by 
tension, and sometimes by crushing. Fig. 31 

[166] 




Fig. 32 — Rupture on Crystal Springs Pipe Line, San Bruno Marsh. 




Fig. 33 — Crystal Springs Conduit between San Mateo and Millbrae. 
Temporary Cut-Off to Stop the Flow of Water toward San 
Francisco and Yet Maintain a Pressure and Supply for the 
City of San Mateo. 



Charles D e r I e t h , Jr. 

exhibits a view of one of the ruptures on the San 
Bruno marsh. Figs. 32 and 33 show other scenes 
along this pipe line during the period of repair im- 
mediately following the earthquake. Redwood 
planks were used for the temporary sills and string- 
ers because larger timber was not quickly available. 
The Pilarcitos conduit for a considerable distance 
practically coincides with the main fault line. In- 
deed, one might almost imagine that the break in 
the ground was purposely staked out along the 
pipe line, or vice versa, from a point somewhat be- 
low San Andreas dam to Frawley gulch, a distance 
of six miles. In this length the conduit is 30-inch 
laminated wrought iron pipe, about 3-16 inch in 
diameter. The center line of the pipe is usually 
found about three or four feet beneath the ground. 
In these six miles of length the pipe was ruptured 
in a great many places, at one place by tension and 
at another by compression. The direction in which 
the pipe line crosses the fault determined whether 
the pipe was torn apart or telescoped. Nineteen 
ruptures were observed by me from a point near 
the northern end of San Andreas Lake to Frawley 
gulch, a distance of about three miles. All rup- 
tures occurred at transverse riveted joints. There 
were some places where the pipe collapsed; in one 
instance, for a length of about fifty feet. There 
were no doubt many more ruptures in this length 

[169] 



<? h e California "Earthquake of i g o 6 

but they had not been uncovered. At tensile breaks 
the pipe was pulled apart by amounts varying from 
almost nothing to as much as five or six feet. At 







W : - 




Fig. 34 — Rupture on Pilarcitos Pipe Line near North End of San 
Andreas Reservoir. 

compensating places the pipe was telescoped by 
similar amounts. Fig. 34 shows a break in this 
pipe line near the up-stream end of San Andreas 
Lake. The pipe at this point was pulled apart 53y 2 
inches. A property fence, Fig. 6, which crossed 

[170] 



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the pipe line about ten feet to the south of this rup- 
ture, was offset seven feet along the fault line, the 
two parts of the fence remaining straight and par- 
allel to their original direction. At Frawley gulch 
the conduit crossed a timber trestle heavily built, 




Fig. 35 — Collapsed Trestle at Frawley Gulch, Pilar citos Pipe Line, 
Spring Valley Water Company. 

about 100 feet in length and some 25 feet in max- 
imum height. Some of the timbers of this trestle 
were partly decayed, but the structure certainly 
was not weak. This trestle was about % mile to 
the east of the fault line. Nevertheless the shock 
was so severe that it entirely demolished the trestle 
and pipe which it carried. The trestle probably 
vibrated in a vertical plane normal to its length, 

[171] 



tf h e California Earthquake o f i g o 6 



and was thrown down-stream to the southeast, as 
shown in Fig. 35. 

From Crystal Springs reservoir to Lake Merced 
the surface of the ground usually is what is known 
as black adobe land. In places it is yellow adobe 




Fig. 36 — Telescoped Rupture, Pilar citos Pipe Line, Spring Valley 
Water Company. 

and sometimes it is a mixture of the two. The 
series of ruptures in the Pilarcitos pipe line to 
Frawley gulch inclusive are therefore found upon 
firm ground unlike the material at the San Bruno 
marsh. The destruction was due to the proximity 
of the fault line or actual coincidence of the pipe 
line therewith, and as has been repeatedly shown 
by the evidence of this paper, construction no mat- 

[ 172] 



Charles D e r I e t h , 



J 



ter how good was unable to withstand the stresses 
along the fault. 

I have not examined the Pilarcitos pipe line 




Fig. 37 — Diagonal Ruptures, Pilarcitos Pipe Line, Spring Valley 
Water Company. 

beyond Frawley gulch to the city, but ruptures 
were probably not so numerous nor so serious in 
this length. The same remark applies to that por- 
tion of the Pilarcitos pipe line near Pilarcitos res- 
ervoir. The Pilarcitos conduit must be abandoned. 

[i73] 



tf h e California Earthquake of i g o 6 

Figs. 36, 37, 38 and 39 show additional ruptures 
in the Pilarcitos pipe line between San Andreas 
Lake and Frawley gulch. In Fig. 36 the pipe line, 




Fig. 38 — Diagonal Rupture, Pilarcitos Pipe Line, Spring Valley 
Water Company. 



supported on a timber framing, crosses a small 
swale. The pipe was telescoped 41 inches, and the 
blow-off valve connection was partly ripped from 
the conduit. Fig. 37 shows two ruptures a little 

[i74] 



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to the north of the break in Fig. 36. At the point 
where the man is standing the fault line crosses the 
pipe line at an angle of 45°. The pipe was 
sheared so that its parts are 20 inches out of align- 
ment, and are moved toward each other 40 inches. 




Fig. 39 — Collapse by Compression at a Small Trestle, Pilarcitos Pipe 
Line, Spring Valley Water Company. 



Fig. 38 is a closer view of the same rupture. Fig. 
39 shows the pipe crossing a small gulch. The 
blow-off valve situated at this point was stripped 
from the pipe and thrown ten feet. The pipe 
was telescoped 49 inches and thrown out of align- 
ment, as shown. This rupture strikingly shows 
that the pipe metal was of high quality. 

[i75] 



<¥ k e California 'Earthquake of i g o 6 

The San Andreas pipe line lies between the Pilar- 
citos pipe and the Crystal Springs conduit; it is 
therefore not so near the fault line as the Pilarcitos 
pipe and avoids the marshes in the region of the 
Crystal Springs conduit. Its injuries were relatively 
slight. Only one important rupture came to my 
notice. It was quickly repaired by putting tem- 
porary banding on the pipe. 

All the main conduits of the Spring Valley Water 
Company, with the exception of the San Andreas 
conduit, were considerably damaged, and in the 
fortnight following the earthquake no water 
reached the city from the Pilarcitos, the Crystal 
Springs, or the Alameda sources, although water 
from Pilarcitos might have found its way through 
the waste-way conduit to San Andreas Lake, and 
thence to the city through the San Andreas conduit 
after its repairs. San Andreas Lake temporarily 
became the distributing reservoir for the city and 
probably will so continue in the future. 

It is plain that the water works of the city of 
San Francisco was subjected to a test more severe 
than the hand of man could devise. The water 
supply of a city is a most important matter, and 
ever since the earthquake the water problem has 
been the greatest one of many problems which have 
concerned the citizens of San Francisco. It is not 
surprising therefore that much concern was ex- 

[176] 



Charles D e r I e t h , Jr. 

pressed about the water situation, and it is readily 
appreciated that the earthquake task of the Spring 
Valley Water Company was neither small from an 
engineering standpoint nor enviable from the mu- 
nicipal and political side. The destruction to the 
Spring Valley Water Company's plant as outlined 
above was produced by nothing less than a cata- 
clysm, something which the mind of man could not 
foresee, and whose effects no engineering structure 
no matter how good could resist. The Crystal 
Springs conduit was of excellent design, but it was 
doomed on the marshes. The Pilarcitos pipe line 
had to succumb; it was right on the line of fault 
for a length of six miles. In the future it will be 
wise to avoid marshes and made ground for im- 
portant pipe lines, and flexible joints should be 
introduced at intervals. The city was saved a ter- 
rible water famine simply because the San Andreas 
conduit, with slight repairs survived the general 
destruction. For safety the city needs a number of 
sources of water, in localities widely separated and 
not in the same geological region, with a number of 
main conduits so arranged that they will not tend to 
be destroyed all at the same time. The Spring Val- 
ley conduits have answered these requirements in 
so far as one of their number survived. 

Buildings and other structures in San Francisco 
to a great extent have been notoriously poor. The 

[1/7] 



tf h e California Earthquake of i g o 6 

same is true in other cities in the earthquake belt. 
The time is ripe for the people to realize that they 
must enforce proper building laws and a proper at- 
titude toward healthy construction both in munici- 
pal and in private works. The works of the 
Spring Valley Water Company are relatively of an 
exceptionally high type of construction. Its 
wrought iron conduits after thirty years of use, even 
in their present demolished condition, exhibit sur- 
prising preservation. Its pumping stations have 
survived where nearby structures collapsed. The 
Crystal Springs dam needs no praise. The earth 
dam at San Andreas fulfills its functions as well as 
ever, although it was directly on the line of the 
main fault and was greatly scarred. Faulty work 
and weak engineering construction may be found 
in other States of the Union, as well as in Califor- 
nia. The engineer and contractor are not alone to 
blame, and I am not willing to criticize them. The 
community itself is partly responsible, because it 
expects and demands too much for its money. 

I have already alluded to the destruction of water 
pipes within the city. Had the main conduits re- 
mained intact, there would still have been great dif- 
ficulty in fighting the fire. Small reservoirs within 
the confines of the city should be connected with 
the main conduits by pipes of considerable size in 
no way connected with nor dependant upon the 

[178] 



Charles D e r I e t k , Jr. 

gridiron system of the streets. Had the city res- 
ervoirs of San Francisco tapped the large conduits 
independently of the street mains, some of the de- 
lay in obtaining water and fire pressure in the first 
fortnight after the earthquake might have been 
eliminated. Within the city confines also there 
should be larger reservoirs than are now provided. 

Within the city boundaries, main branch pipes, 
and in general the pipes of the gridiron system 
were much destroyed. In the softer and made 
ground this was especially true. Moreover, the great 
extent of the fire destruction left innumerable tap 
and service pipes to hundreds of burned buildings 
in a most dilapidated condition. Explosions of gas 
mains, Fig. 40, added further rupture to the streets 
and the pipes beneath them. With this general 
demoralization of the gridiron system within the 
city and the loss of the Pilarcitos and Crystal 
Springs conduits, the situation on the morning of 
the earthquake may be understood. There was lit- 
tle water in the city and no water pressure. 

Earthquakes are not uncommon in California and 
they will naturally occur again. There has been 
much talk of tapping the water sources of the Sierra 
Nevada Mountains and bringing that water to San 
Francisco by conduits and water courses which 
must be nearly 200 miles in length. As already 
stated, it is to be desired that the city have a num- 

[ i79] 



The California Earthquake of i g o 6 

ber of distinct sources of water, but in the light of 
our present catastrophe how much more danger 
must there be of earthquake destruction upon a 
line of so extended a length? Conduits in duplicate 
would be of no avail; when one breaks so will the 




Fig. 40 — Gas Main Explosion, Valencia Street, near Market Street, 
San Francisco. 

other. The only safeguard will be two distinct con- 
duits running in widely separated districts, but such 
a proposition would entail great cost. 

PALO ALTO 

Palo Alto is seven miles east of the fault line; its 
important earthquake damage occurred on the 
Campus of Stanford University. The extent of this 

[180] 



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destruction was great. The grade of workmanship 
on the University buildings was of relatively high 
quality, especially for the older buildings. The 
original buildings were planned with regard to 
earthquake possibilities. Steel-frame construction 




Fig. 41 — Arcade, Inner Quadrangle, Stanford University. 

on the Pacific Coast was in its infancy at the time, 
and reinforced concrete almost unknown every- 
where, therefore the earliest Stanford buildings and 
the inner arcades were built by day labor, with 
heavy cut stone and mortar rich in cement. The 
outer arcades and buildings, built later, were faced 
with ashlar and backed with rubble, too often im- 
properly mixed with mortar. The structures built 

[181] 



tf h e California Earthquake of i g o 6 

since 1902 were mostly unfinished in April, 1906, 
and were made of brick, thinly veneered with stone. 
A number of them contained some steel framing in 
domes or roof trusses, which, in vibrating, only 
helped to throw down the surrounding masonry 




Fig. 42 — Rear View Memorial Arch, Stanford University, Showing 
Arch Ring Intact. 



walls. The earliest structures built remained essen- 
tially uninjured, except where they were too high, 
as in the case of the church and arch, but the latest 
additions were severely wrecked or destroyed, as 
they deserved. The central part of the Museum 
and Roble Hall were built of reinforced concrete, 
being among the first instances where that material 

[182] 



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was used. This construction was uninjured except 
for the falling of plaster. 

I attribute the excessive destruction to three 
causes: (1), the nature of the ground; (2), the near- 
ness to the fault line, and (3), the type of construc- 




Fig. 437- Fallen Masonry from Top of Memorial Arch, Stanford 
University, Showing Mortar Strength. 

tion. I consider the third reason by far the most 
important. Heavy stone-faced buildings of the 
type we find at Stanford, no matter how well built, 
cannot resist an earthquake of the intensity experi- 
enced at Palo Alto, when we consider the nature 
of the ground upon which the buildings rest. Top- 
heavy stone arcades and walls, supported by light 
masonry pillars, see Fig. 41, are not constituted to 

[ 183 ] 



tf h e California Earthquake of i g o 6 

withstand vibration, especially when the roofs are 
covered with heavy tile. The interior framing, 
especially of the later Stanford buildings, generally 
lacks the unity and stiffness which can come only 
through steel-cage construction or the best type of 
reinforced concrete cage construction. Consider- 
ing earthquakes, I do not think the main type of 
structure at Stanford was happily chosen. The 
type lacks unity and coherence of frame. The 
buildings are rigid and often too high. The fault 
is more in the type of design, and not so much in 
the execution. 

I have seen many pictures of the Memorial Arch 
showing dramatic destruction. These pictures 
give a false impression. Fig. 42, a view of the rear 
elevation, shows that the arch ring itself was not 
thrown down; in fact, there were but a few cracks 
in the crown of the soffit. It was the heavy top and 
cornice, insufficiently tied, that fell, as they should. 
It would have been surprising had they not fallen. 
Above the arch was a large box-shaped mass of 
masonry upon which rested the heavy overhanging 
cornice, and this box had practically no transverse 
framing or partition walls of any kind. The masses 
that dropped from the arch fell in large pieces, 
nearly 100 feet to the pavement without crumbling, 
Fig. 43, which proves that the mortar was good. 
Considerable cement was used in the mortar for the 

[184] 



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Memorial Arch. Perhaps not so much, but at least 
a goodly amount of cement, was used in every 
building which I examined. 

In my opinion, had Stanford's buildings been of 
reinforced concrete, or of a good type of light brick 




Fig. 44 — View at Agnews Showing the Complete Collapse of the 
Main Tower of the Asylum. 



or stone construction, bound to a yielding but 
unified metal frame, there would have been practi- 
cally no destruction. The type of building should 
emphasize coherence and lightness, combined with 
yielding and elasticity. Moreover, it is a mistake 
to erect university and school buildings more than 
two stories in height; it is unwise for earthquake 

[185] 



*{ k e California Earthquake of i g o 6 

conditions and inappropriate for halls of 
assemblage. 

AGNEWS ASYLUM 

Six miles to the north of San Jose one finds the 
Agnews Insane Asylum, consisting of one large 



f 


\ 






-,. n 






WBm V3m 


t fl 


• 


1 




>;!HOU';AH tall 


1 a ; " 

f i jkl * 


B 3 c B 


> 

>- - 


. 


^^M^F 






'*y' ! J$m 


SrgS^sS 



Fig. 45 — Earthquake Destruction, Native Sons' Hall, San Jose. 

brick, timber framed, building about two city 
blocks in length, surrounded by some twenty 
similar but smaller brick structures. One hundred 
patients and eleven help were killed the morning 
of the earthquake. I do not know how many were 
injured. Not one of all these buildings remained 
habitable. Of all the destruction that I saw, and 

[186] 



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I visited the whole disturbed area, this cluster of 
buildings exhibited the most complete earthquake 
destruction, with the possible exception of the City 
Hall buildings in San Francisco. They are both 
public structures. Is it not time for California 




Fig. 46 — A View on First Street, San Jose, Showing Lack of Fram- 
ing for First Floor. These Buildings Were Later Pushed Back 
into Place. 



seriously to realize the situation? The main central 
brick structure and tower of Agnews Asylum, 
Fig. 44, entirely collapsed. The central tower fell 
en masse and crumbled to pieces so that three 
distinct wings of the buildings, themselves much 
demolished, were left disconnected. Some of the 
outer, smaller buildings had nine-inch brick walls 

[187] 



^ h e California Earthquake of i g o 6 

for a height of two stories or more. It is significant 
to observe that a high water tower of structural 
steel, situated close to the power house of the 
asylum, remained entirely intact. The power house, 
built of brick, and its high brick chimney, collapsed 
with the rest of the brick structures. 

SAN JOSfi 

San Jose, about forty miles to the south and east 
of San Francisco, is thirteen miles to the east of the 
fault line. This city fortunately was spared a con- 
flagration. The earthquake destruction was ap- 
palling, as is shown by a few typical photographs; 
see Figs. 45, 46, 47, and 48. 

San Jose's water works, like that of Santa Rosa, 
was not injured; its sewers also were left intact, 
showing that there was no unequal displacement 
of the ground. The earthquake destruction was 
the result of severe vibration of poorly constructed 
brick and stone buildings. Again we find cheap 
construction with lime mortar, weak framing and 
insufficient anchoring for floors and roofs. Whole 
sides and fronts of two and three story store and 
office buildings on the main business streets col- 
lapsed; Fig. 45. On First Street, in the main 
business center, in one instance, a row of about six 
or seven buildings careened, due to a lack of suf- 
ficient transverse framing in the first story. Stores 

[188] 






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occupied these main floors, demanding large win- 
dow openings and as much floor space as possible. 
Virtually the upper portions of the buildings rested 
on stilts; see Fig. 46. Public buildings in San 
Jose, with the exception of the postoflice, were 




Fig. 47 — Hall of Justice, San Jose, Completed in 1905. 



generally racked. The tower of the postoflice was 
thrown down. In too many instances we find heavy 
stone facings improperly anchored to the interior 
frames, and roofs without system. In the great 
area of destruction, one finds roofs depending for 
their support upon the stiffness of the walls upon 
which they rested, while from the nature of design 
and construction the walls lacked stiffness. These 

[189] 



C T h e California Earthquake of i g o 6 

flimsy or clumsy roofs, when subjected to earth- 
quake vibration, tended to lower in the peak and 
to spread at the ends. Naturally they crushed out 
the weak outer walls, lacking in bond and inher- 
ently weak in mortar. Nearly all the public build- 




Fig. 48 — Rear View, Hall of Records, San Jose, Showing How the 
Heavy Stone Outer Walls Cracked Away from the Interior 
Framing Due to Improper Anchoring of Walls to Floors and 
Roof. 



ings, most of the school houses, and many churches 
in San Jose, where built of stone and brick, were 
demolished or severely damaged. Some of these 
structures still stand, but if wisdom is exercised, 
most of them will be torn down. Even some frame 
buildings, notably churches and the annex to the 

[ 190] 



Charles 



D e r I e t h , 



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Hotel Vendome, improperly framed and with weak 
underpinning, completely collapsed; see Fig. 16. 



PAJARO BRIDGE 



The Pajaro Bridge is perhaps the most interest- 
ing structural example of violent earthquake effect. 



h ■- . • 












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.*j. 






'mJSM%k* 



Fig. 49 — Pajaro River Bridge, Southern Pacific Railroad; Tempo- 
rarily Strengthened by Timber Bents and False Work; View 
Taken May 30, 1906. 

It is on a six-degree curve whose chord makes an 
angle of about 40° with the fault line. The 
fault crosses the bridge near the west end. The 
bridge consists of two end deck-plate girder spans 
of fifty feet each, and four intermediate deck Pratt 
trusses, each of 120-feet span; Fig. 49. The abut- 

[191] 



'the California Earthquake of i g o 6 

ments and the intermediate piers are of concrete 
with granite copings. This structure, in my judg- 
ment, would not have been affected by the earth- 
quake had it been at a reasonable distance from the 
fault line, but it was subjected to a most severe 




Fig. 50 — West Abutment, Pdjaro River Bridge, Southern Pacific 
Railroad. 

racking, since the ground upon which its piers 
rested moved unequally. The distance between 
the end piers was increased 3^2 feet. All the piers 
and abutments were moved more or less, but the 
heaviest movements occurred at the west end of 
the bridge. Fig. 50 shows the west abutment 
where the steel plate girders were moved 24 inches 
off the abutments and had to be supported by a 

[ i9 2 ] 



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temporary wooden bent. The plate girder span 
resting on this abutment did not fall during the 
earthquake, although it was dragged off the bridge 
seat, because it was held up by the rail fastenings 
and the riveted connections to the next span to the 



i £ iPflf £ : €i 


im i \ 


ft* 


^m ' ~h-M 









Fig. 51 — First Intermediate Pier, West End, Pdjaro River Bridge, 
Southern Pacific Railroad. 



east. Fig. 51 shows the first intermediate pier 
at the west end of the bridge. This pier near its 
base was ruptured in a horizontal section, probably 
a level between two days' concrete work. The 
mass of the pier above the rupture was moved east- 
ward about three inches with respect to the base. 
The coping was ripped from the top and moved 



i93 



The California Earthquake of i g o 6 

eastward relatively more than 20 inches. The 
segmental rollers and the steel pedestals upon the 
coping were smashed and the anchor bolts severely 
bent. The next intermediate pier leaned somewhat 
to the east, and the anchor bolts above the coping 
were bent so that the pedestals of the steel work 
were moved some three inches. The distortion was 
less as one approached the eastern end of the 
structure. The eastern abutment was considerably 
cracked. The whole bridge superstructure was 
thrown slightly out of plumb. Earth motions are 
clearly seen in Fig. 50, where the sloping earth 
was moved 18 inches along the side wall of the west 
abutment. 

SALINAS HIGHWAY BRIDGE 

The Salinas River runs through a marshy district 
of river deposits of slight elevation above the sea 
level. Although the region is at a distance of ten 
to twenty miles from the fault line, there was much 
evidence of differential surface movement, distinct 
from elastic vibration, just as in many other instan- 
ces of soft surface deposits, for example, the San 
Bruno marsh near South San Francisco, where the 
Crystal Springs pipe line of the Spring Valley 
Water Company was so badly ruptured. The land on 
the south bank of the Salinas River, for a consider- 
able area, was moved into the river in a northerly 

[ i94] 



C h 



I e s 



D 



I 



t h , 



J 



direction a distance of about six feet. Fig. 52 
shows the south abutment of the Salinas highway 
bridge. The ground under the superstructure 
moved about six feet, careening the pile foundations 
as shown in the picture, without seriously injuring 




Fig. 52 — South Abutment, Salinas Highway Bridge. 



the trusses. A three-inch oil pipe line which crossed 
the bridge was ruptured on the south approach, one 
length of pipe being bent to form the letter "S." 
The northern approach to the bridge was hardly 
affected. In fact, the northern bank of the river 
shows little disturbance at this point. From the 
Salinas bridge eastward, a distance of about 1^ 
miles to Spreckels, the south bank of the river is 

[i95] 



< f h e California Earthquake of i g o 6 

continuously scarred and rent so that a wagon road 
was made impassable for vehicles. 

THE SPRECKELS SUGAR MILL 

At Spreckels is found the Spreckels Sugar Mill. 
The mill buildings are of excellent construction. 
The main building, about 100 x 500 feet, a huge 
box-shaped structure with heavy steel frame, brick 
walls supported on the frame, and arched concrete 
floors with steel floor framing, rests on a pile foun- 
dation. The mortar for the brick work is excellent 
and contains considerable cement. Had these 
buildings been in Santa Rosa or San Jose, I think 
they would have stood the earthquake with possibly 
a few slight cracks and the loss of some brick here 
and there near the cornices and corners. But un- 
fortunately they rest on soft ground, very much 
like the made ground areas of San Francisco. Con- 
siderable portions of the brick walls were thrown 
out of the steel frames. The long walls of the main 
building are supported by steel columns about every 
15 feet and are braced transversely at these columns 
by the interior framing; except in the middle third 
of the building, where there is an open space from 
ground to roof to give clearance to the huge 
machinery. In this middle third, where the long 
walls are not laterally braced by interior transverse 
frames and floors, the walls were badly buckled. 

[ 196 ] 









-,, 










4^" ' 






i 




'1 


. 








."": 


if 




jj^^ga&&/;_ 


• - - 





















Fig. 53 — West Wall, the Spreckels Sugar Mill, near Salinas, Showing 
Bulged Wall and Brickwork Thrown from the Steel Frame. 




Fig. 54 — North Wall, the Spreckels Sugar Mill, near Salinas, Show- 
ing Ruptured Brick Curtain Walls and the Advantages of a 
Class A Steel Frame. 



C h 



I 



D 



I 



t h , 



J 



The east wall was buckled concave outward, 
and was badly cracked, but little of it fell. The 
west wall, in the middle third, was buckled convex 
outward, and naturally the brick work was thrown 
down in large masses. Fig. S3 shows the west 











'J 


''■ma 



Fig. 55 — Ruptured Conveyor, the Spreckels Sugar Mill, near Salinas, 
Showing Slipping of the Ground into the River. 

wall of the building. I believe this building was 
subjected to an earth movement from south to 
north, which accounts in a measure for the buckling 
of the long walls in the middle unsupported third. 
There may have been some settling of the walls 
also. Large masses of brick in the north wall, Fig. 
54, were thrown down. Fig. 55 shows a rup- 
ture in the carriage way to the dumps at the south 



199 



tf h e California Earthquake of i g o 6 

end of the structure, clearly showing the existence 
of a decided ground movement at the time of the 
earthquake. All the smaller buildings were damaged 
to some extent. The Spreckels Sugar Mill was 
well designed. It was probably subjected to a more 
severe racking than any other well designed struc- 
ture in the State. It can readily be repaired and 
speaks for the stability of Class A construction. 

CONCLUSIONS 

There has been much comment of late regarding 
the relative merits of sea level and lock types of 
canal for the Isthmus of Panama, in the light of 
earthquake possibilities. From a study of the 
earthquake destruction to San Francisco buildings 
it would appear that honestly, scientifically and 
generously constructed works can abundantly with- 
stand any reasonably severe earthquake shock so 
long as the structure does not happen to exist on 
a fault line or a place of very unequal motions of the 
ground. On a fault line no structure can fully with- 
stand the shock, no matter how well built. If for- 
tunately located, however, a structure on or near a 
fault line may not be seriously crippled. In their 
severe locations it is seen that the 93-foot San An- 
dreas earth dam still fulfills its functions and the 
Pajaro bridge, though badly crippled, was speedily 
made usable; the Spreckels Sugar Mill was repaired 

[ 200 ] 



Charles D e r I e t k , Jr. 

without great expense, and large well built build- 
ings on honestly designed and deep foundations 
stood the racking on the made ground in San Fran- 
cisco. In the future, water supply conduits should 
avoid fault lines, marshes, and other unstable 
ground whenever possible. Dams should not cross 
fault lines, and when possible should not be run at 
right angles thereto; yet considering their purpose 
it usually will be necessary to place dams in the 
most unsatisfactory positions. It is not wise in 
earthquake countries to build bold arch dams of 
thin construction. Important railway bridges 
should be located at river crossings not coincident 
with lines of crustal weakness, and should avoid 
soft alluvial deposits. It is easy to state this ad- 
vice and these restrictions, but it is another thing 
to follow them. The locating engineer is not al- 
ways free to choose his site. Where structures 
must be built upon treacherous ground or near 
fault lines, no expense should be spared for good 
materials, high grade workmanship, and intelligent 
design. The most generous factors of safety should 
be used and the best designing talent employed. 
California engineers can not pay too much atten- 
tion to geologic structure. 

Careful examination of all types of structures 
within the earthquake belt leads me to emphasize 
the following detailed conclusions. I do not expect 

[201 ] 



°t h e California Earthquake of i g o 6 

every one to agree with them. Some of the state- 
ments may be very radical, and some may be 
wrong: 

1. Cornices and top walls of buildings, especi- 
ally of brick and stone structures, should not be 
heavy nor have great projection. In the future 
cornices and top walls should be more securely 
anchored with metal, their masonry bond should 
be made with care and the cementing materials 
should be of high quality. A considerable number 
of lives were lost by falling brick and stone from 
such sources. These parts of buildings have been 
very generally demolished by the earthquake. 

2. Cornices and top walls of first class steel 
cage constructed buildings, where the steel fram- 
ing and anchoring has been carried into the cornice 
work, have resisted the earthquake. 

3. Projecting brick work and fire walls of ordi- 
nary brick and stone structures have proven them- 
selves an abomination, especially where lime mor- 
tar was used. With cement mortar the destruction 
was nearly as great, the only difference being that 
the material fell in large masses. 

4. Brick chimneys for ordinary brick or frame 
dwellings should be built of weak lime mortar 
above the roof line. This seems a paradoxical 
statement. In a severe earthquake the brick chim- 
ney will not move with the house. It must col- 

[ 202 ] 



Charles D e r I e t h , Jr. 

lapse. If built with rich cement mortar it will fall 
fall in one piece and crush through the roof. If 
built of lime mortar it will crumble and the indi- 
vidual bricks will roll off the sloping roof. Metal 
chimneys should be studied for the part above the 
roof line. If brick is insisted upon from preference 
or custom, reinforce the brickwork with steel rods 
and bands. 

5. Terra cotta and similar materials should not 
be used so profusely and boldly in the future. They 
are not good earthquake materials. They have 
been badly cracked by earthquake vibration. The 
north wall of the Fairmont Hotel, where it is faced 
with terra cotta, was badly cracked. Pressed brick 
work with good mortar and good bond is a far 
more satisfactory material. Terra cotta orna- 
mentation on the Mills Building and many other 
buildings was badly spalled by vibration. I would 
not eliminate terra cotta from use, but it should be 
less highly ornamented, be manufactured with 
greater thickness, and the hollows should be filled 
with a cementing matrix. 

6. Hollow tile partitions in the General Post- 
office were almost wholly destroyed by the earth- 
quake. Of course this building rested upon very 
treacherous ground, but the earthquake certainly 
did very much more damage to tile partitions in 
San Francisco than is generally admitted. These 

[203! 



C Z J h e California Earthquake of i g o 6 

partitions have little strength and are readily col- 
lapsible. They have no elastic continuity. 

7. I believe hollow tile floors were less disturbed 
by the earthquake than tile partitions, because 
there was less tendency to unequal motion in the 
plane of the floor; whereas partitions were subject 
to a greater racking motion. Tile partitions and 
floors do not appeal to me with the same force as 
reinforced concrete construction, especially when 
the question of fire-proofing is left out of the 
discussion. 

8. Brick buildings without steel work and of 
light construction should have small height, three 
to four stories at most. Their bond of brick work 
should be carefully inspected and their brick walls 
should be securely tied to the floor and roof frames. 
On soft ground their foundations should be even 
more carefully designed for stiffness of framing 
and distributing power than those for wooden 
buildings. The bond of brick work in San Fran- 
cisco was proverbially bad. 

9. Cheap lime mortar should not be allowed for 
buildings in the congested districts of San Fran- 
cisco. Cement with just enough lime to make it 
workable — say one part cement to four or five of 
lime mortar — should be more generally insisted 
upon, not only in the congested parts of the cities, 
but everywhere where brick buildings are used. 

[204] 



Charles D e r I e t h , Jr. 

The high school building at Berkeley may be 
taken as an example of lime mortar building. It 
was most seriously cracked, especially in the sec- 
ond story. Hundreds of buildings might be named 
in this connection. In the light of what has hap- 
pened it is a crime to use bad bond and lime mortar 
for brick work in schools and public buildings, in 
fact in all buildings. Mortar has been too generally 
applied to dry brick. 

10. Brick buildings of greater height than four 
stories should have heavy walls and a sufficient 
number of interior cross walls to give lateral stiff- 
ness. The Appraiser's Building or Custom House 
was unharmed by the earthquake. The Palace Hotel 
stood the shock splendidly, the latter being an ex- 
cellent type of brick structure, whose brick walls 
were reinforced with iron rods. The foundations 
of such buildings should be designed with the great- 
est care to prevent unequal settlement. 

11. All over the earthquake belt one found brick 
and stone structures badly demolished by the fall- 
ing out of main walls due to improper design of the 
roof trusses. These trusses too generally were of 
clumsy wood construction improperly anchored to 
the supporting walls and unscientifically framed. 
Too generally they were lacking in a lower chord 
tension member. The earthquake caused such roofs 
to spread and kick out the walls, which had no 

[205] 



T h e California Earthquake of i g o 6 

ability whatever to resist a lateral thrust. The 
high school building in Berkeley is a typical ex- 
ample. For large school buildings roof trusses of 
steel should be used. One saw many cases where 
brick walls stood the shock that would have been 
thrown down except for the tying property of the 
roof trusses above them. The Majestic Theatre in 
San Francisco clearly showed how steel trusses 
kept high walls from collapsing. 

12. Properly constructed wooden buildings 
withstood the earthquake with the exception of 
their brick chimneys, no matter where located in 
the earthquake belt, except on the fault line and in 
regions of the greatest disturbance on soft ground. 
Some frame buildings collapsed upon favorable 
ground due to improper underpinning. There 
should be more continuity in the frames of wooden 
buildings, especially at the floor levels, and the 
underpinning should be more carefully attended to 
in the future. 

13. At the time of the earthquake there were 
entirely too many top-heavy and improperly braced 
brick and stone towers and steeples in San Fran- 
cisco and other cities. Where they are merely or- 
namental, mere masonry, towers should be dis- 
couraged as far as possible. Their ruins were 
everywhere to be seen in San Francisco, Oakland, 
Santa Rosa and San Jose. The Ferry tower might 

\2o6^ 



Charles D e r I e t k , Jr. 

have had heavier framing, although it should 
hardly be spoken of in this connection. Most 
towers lack in interior cross walls and in necessary 
steel frames. The Memorial Arch at Stanford 
University has been referred to. Reinforced con- 
crete, where not too boldly employed, is well 
adapted for these purposes. 

14. Important buildings like the Postoffice 
should not be placed on filled ground or treacher- 
ous ground, but when they must be so placed, they 
should have heavier steel framing and lighter 
masonry work than the Postoffice. The type of 
building structure to be selected in these cases 
should be determined by the nature of its founda- 
tion site. Remarks which I have made concerning 
buildings at Stanford University are here pertinent. 

15. High buildings with deep pile foundations 
of the proper design withstood the earthquake 
shock well on soft ground. Considering the nature 
of the material on which the Ferry Building rests, 
it stood the shock splendidly because of its excel- 
lent pile foundations. The Call Building founda- 
tion represents the slab type, apparently equally 
well fitted for service. 

16. Reinforced concrete cage construction should 
be more respected in the future by the building 
laws and trades unions of San Francisco. There 
is no reason why buildings of this type, designed 

[207] 



*? h e California Earthquake of i g o 6 

by competent engineers, should not be at least six 
or eight stories in height. 

17. Low buildings of intelligent reinforced con- 
crete construction are far more able to resist earth- 
quake shock than brick and stone buildings. 

18. On soft ground the footings of ordinary 
buildings too light to require pile foundations 
might have cellar slabs of reinforced concrete to act 
as units with the wall footings to give distributing 
power and prevent unequal settlement. 

19. Reinforced concrete sewers should be 
studied in the light of brick sewer destruction in 
the made ground of San Francisco. 

20. Important water mains should avoid soft 
ground and when they must necessarily pass from 
firmer to softer ground they should be provided 
with flexible joints and cut-offs. 

21. Important water mains on which the fire 
service depends, which must run through the made 
ground of the city, should be of riveted wrought 
iron or steel, have flexible joints at intervals and 
be lodged in tunnels, say of reinforced concrete. 
Earthquake disturbance near the water front might 
severely crack such tunnels without great injury 
to the pipes within, due to the properties of the 
materials, the nature of the pipe joints, and the 
clear space between the tunnel walls and the pipe. 
Such a construction would further give more 

[208 1 



Charles D e r I e t h , Jr. 

probability of access to the pipe in case of calamity. 
Important networks of pipes in the gridiron system 
should be arranged in more or less independent 
units with respect to the softer and firmer grounds 
of the city; so that flow in the pipes on made ground 
could be quickly separated from that on more solid 
foundations. 

22. Main conduits running from storage res- 
ervoirs to the city should avoid marshy lands as 
far as possible. Where they must necessarily cross 
swamps and marshes, they should be provided with 
flexible joints and not be too firmly blocked to their 
platforms. 

23. The city should have a number of sources 
of supply in widely separated localities of distinct 
geological formation. 

24. Equalizing reservoirs within the confines of 
the city should be numerous and of considerable 
capacity. 

25. Small distributing reservoirs within the city 
limits should be connected with the main conduits 
by large pipes independent of the gridiron system. 
These pipes should be carefully designed and be 
easy of access. With such provision, some of the 
delay incident to the forcing of water through crip- 
pled street mains to the various city reservoirs and 
pumping stations might have been avoided. Arte- 

[209] 



tf h e California Earthquake of i g o 6 

sian wells should be encouraged as local sources 
of supply. 

26. The business district should be safeguarded 
by a salt water system in addition to the regular 
water supply for fire service, and where salt water 
pipes must run through made ground they should 
be provided with flexible joints and with a tunnel 
construction as has been suggested for the main 
water pipes; or they should be on the surface. 

27. San Francisco needs a fire boat service. 

28. High brick chimneys for factories should be 
built with cement mortar; even then they should 
be reinforced. In many cases a lower chimney 
with a forced draft should be considered. A study 
of reinforced chimneys should be made. They 
would withstand earthquake shocks much better 
than brick ones. 

29. In the business section of the city Class A 
buildings and first class reinforced concrete struc- 
tures should be encouraged at the expense of Class 
B structures, and the skimping of steel frames 
should meet with entire disapproval. Diagonal 
framing should be introduced wherever windows 
and interior passage ways or openings do not 
prevent; better still, heavy knee braced framing 
and spandrel girder framing should receive more 
attention. 

[210] 



Charles D e r I e t h , Jr. 

30. The design of high buildings with self-sup- 
porting walls should be discouraged. 

31. Steel columns should run through more 
than one floor, and their splice joints should be 
strongly designed. 

32. Cast iron columns should not be used. 

33. Heavy stone ornamentation should not be 
hung to the steel frames of high buildings, and 
heavy centralized supports on the first floor, as in 
the Flood Building, should be avoided when pos- 
sible. No expense should be spared for founda- 
tions of buildings of great height. 

34. Heavy stone corner piers at the sidewalk 
level of steel framed buildings should rest upon the 
frame and not upon masonry walls under the side- 
walk. Where such piers rested upon concrete under 
the sidewalk, the stone work was badly cracked; 
where they were supported by the steel frame no 
cracks were found. 

35. Face brick should be carefully bonded to the 
back brick in Class A buildings. Large areas of 
face brick fell from the west wall of the Merchants 
Exchange Building because of improper bond. 

36. Reinforced concrete buildings of careful, 
honest, and intelligent design should be allowed to 
enter competition in San Francisco. It is unfor- 
tunate that reinforced buildings have been placed 
in the Class B list. To the layman this implies 

[211] 

\ 



< f h e California Earthquake of i g o 6 

inferiority to Class A structures. Of their types 
Class A buildings are not to be considered better 
than first-class reinforced concrete cage constructed 
buildings, only I should not use the latter type for 
structures of the greatest height. 

37. Neglecting the problem of surface appear- 
ance, Class A buildings might be designed with 
curtain walls of reinforced concrete instead of 
using brick and terra cotta. 

38. High buildings like the Mills Building in 
which the floors are supported on a steel frame, but 
whose walls are self-supporting, should not be 
imitated in design in the future. When such build- 
ings are badly shaken, or when their outer walls 
are badly damaged, repair is difficult. In Class A 
buildings, where the steel frame carries the load 
of each floor independently, such difficulty vanishes. 
The Mills Building had the further miserable fea- 
ture of columns breaking joints at every floor. 

39. Electric insulation for high tension trans- 
mission should be rigorously inspected. Chim- 
neys on cheap brick and frame dwellings should be 
more sensibly built. Electric wires and bad chim- 
neys were fruitful sources for the starting of fires 
immediately after the earthquake. 



[212] 



The Investigation of the California 
Earthquake 



By 

Grove Karl Gilbert 

Of the U. S. Geological Survey 



Published by permission of the director of the United States 
Geological Survey and of the chairman of the California Earthquake 
Investigation Commission. 



V 



Karl G i I b 



these two centers of organization; but as the needs 
of the hour were patent to all, the work was not 
prejudiced by the lack of intercommunication. 

On the third day after the shock Governor 
Pardee appointed a State Earthquake Investiga- 
tion Commission, naming as its chairman the head 
of the geological department of the State Univer- 
sity, Professor Lawson, and including in its mem- 
bership Professor Branner, of the Stanford Univer- 
sity, Professors Davidson and Leuschner, of the 
State University, Professor Campbell, of the Lick 
Observatory, Mr. Burckhalter, of the Chabot 
Observatory, Professor Reid, of Johns Hopkins 
University, and Mr. Gilbert, of the United States 
Geological Survey. The commission held its first 
meeting three days later, when the scope of its 
work was considered and defined, provision was 
made for circulars soliciting information, an an- 
nouncement was prepared for the purpose of re- 
lieving certain groundless fears entertained by a 
portion of the community, and two committees 
were appointed for the general work of observation. 
To the first committee, with Professor Lawson as 
chairman, was assigned the determination and 
study of surface changes associated with the earth- 
quake and the collection of data as to intensity, so 
that isoseismals, or curves of equal intensity, might 
be drawn upon the map. To the second committee, 

[219] 



*? h e California Earthquake of i g o 6 

with Professor Leuschner as chairman, was as- 
signed the collection of data for the drawing of 
coseismals, or lines connecting points on the earth's 
surface reached by the shock at the same instant. 
Some weeks afterward, when the main features of 
the earthquake had become known, a third com- 
mittee was appointed, with Professor Reid as chair- 
man, to consider the relations of the earthquake 
phenomena to certain problems in geophysics, or 
the science of the inner earth. 

The work of these three committees is still in 
progress, and will not be completed for several 
months. The actual drawing of isoseismals and 
coseismals can not be performed until a large body 
of observations have been compiled and studied, 
and the geophysical problems are as yet only im- 
perfectly formulated; but of the physiographic 
phenomena, or the disturbances of the earth's sur- 
face, so much is known that it has been thought 
advisable to prepare a preliminary report. This 
was submitted to the governor on the third of 
June, and has been issued as a pamphlet of twenty 
pages. The expenses of the commission are being 
met by the Carnegie Institution. 

Architects and engineers were not less prompt 
and energetic. To the men who plan and direct 
construction in the earthquake district of Califor- 
nia it was important to know what materials and 

[ 220 ] 




Fig. 2 — Fault Topography between Tomales and Bolinas Bays; Looking Northwest. 
The General Slope Toward the Left Has Been Interrupted by a Slight Uplift 
of the Part at the Left. The Pond Occupies a Hollow Thus Produced. 



Grove Karl Gilbert 

what structural forms best withstood the shock, 
and they immediately began the study of earth- 
quake injuries and of instances of immunity from 
earthquake effects. In that part of San Francisco 
where the earthquake injury was most serious the 
shock was quickly followed by fire, which destroyed 
much of the evidence, but many important obser- 
vations were made in the brief interval. The study 
of structural questions, like the study of natural 
phenomena, was at first individual only, but after- 
ward was aided by organization. Committees were 
appointed by various professional societies, national 
and local, and were charged with the investigation 
of specific structural questions, and the results of 
their labors will find place not only in the trans- 
actions of the societies, but in revised building 
regulations and in important modifications of 
municipal plants for lighting and water supply. 
Various bureaus of the national government have 
also taken part in the structural studies, sending 
experts to San Francisco and other localities of 
exceptional earthquake violence. 

The Japanese government promptly sent to 
California a committee of investigation headed by 
Dr. Omori, professor of seismology in the Univer- 
sity of Tokyo, and composed otherwise of architects 
and engineers. The first conference of these visit- 
ors with the State Commission warranted the sug- 

[223] 



tf h e California Earthquake of i g o 6 

gestion that we may find it as profitable to follow 
Japanese initiative in the matter of earthquake- 
resisting construction as in that of army hygiene. 

The following sketch of the physical features of 
the earthquake is based chiefly on the body of data 
gathered by the State Commission: 

An earthquake is a jar occasioned by some violent 
rupture. Sometimes the rupture results from an 
explosion, but more commonly from the sudden 
breaking of rock under strain. The strain may be 
caused by the rising of lava in a volcano or by the 
forces that make mountain ranges and continents. 
The California earthquake of April 18 had its 
origin in a rupture associated with mountain-mak- 
ing forces. A rupture of this sort may be a mere 
pulling apart of the rocks so as to make a crack, 
but examples of that simple type are comparatively 
rare. The great majorit}^ of instances include not 
only the making of a crack but the relative move- 
ment or sliding of the rock masses on the two sides 
of the crack; that is to say, instead of a mere frac- 
ture there is a geologic fault. After a fault has 
been made its walls slowly become cemented or 
welded together, but for a long time it remains a 
plane of weakness, so that subsequent strains are 
apt to be relieved by renewed slipping on the same 
plane of rupture, and hundreds of earthquakes may 
thus originate in the same place. From the point 

[224] 







Fig. 3 — This Fence, Previously Continuous and Straight, Was Broken and Parted 
by the Earthquake Fault, the O if set Being 8 J / 2 Feet. The Line of Fault, Con- 
cealed by the Grass, Crosses the Ground from Left to Right, Touching Both 
the Dissevered Ends of the Fence. 



V 



Karl Gilb 



of view of the geologist the displacements of rock 
masses are the primary and important phenomena; 
the faults are incidental phenomena, of great value 
as indices of the displacements; and the earth- 
quakes are of the nature of symptoms, serving to 
direct attention to the fact that the great earth 
forces have not ceased to act. 

A faulting may occur far beneath the surface and 
be known only by the resulting earthquake; but 
some of the quake-causing ruptures extend to the 
surface and thus become visible. The New Madrid 
and Charleston earthquakes are examples of those 
having deep-seated origins, the Inyo and Califor- 
nia, of those whose causative faults reached the 
surface of the ground. 

The general character of California earthquakes 
was so well known that when the dispatches told 
of a severe shock at San Francisco no American 
geologist had a moment's doubt that it was caused 
by a fault movement, and among those specially 
conversant with the structure of the affected 
district attention was immediately directed to 
several fault lines, with the expectation that one or 
more of them would show the marks of fresh dis- 
location. Mr. Ransome prepared a prophetic ar- 
ticle in which he indicated the lines most likely to 
be concerned.* Professor Branner stated in an 



* Nat. Geog. Mag., Vol. 17, 1906, pp. 280-296. 

[227] 



C Z° h e California Earthquake of i g o 6 

interview that he had immediately made a forecast 
of the locality of the origin and that it had proved 
to be correct, and Mr. Fairbanks went at once to 
a zone of "earthquake topography" with which he 
was already acquainted, and found a fresh rupture 
in the expected place. 

The California earth- 
quake was caused by a 
new slipping on the 
plane of an old fault 
which had been recog- 
nized for a long distance 
in California, and in one 
place had been named 
the San Andreas fault. 
Associated with this 
fault is a belt of peculiar 
topography, differing 
from the ordinary topo- 
graphic expression of 
the country in that many 
of its features are directly due to dislocation, in- 
stead of being the product of erosion by rains and 
streams. One of its characteristics is the frequent 
occurrence of long lines of very straight cliffs. An- 
other is the frequent occurrence of ponds or lakes 
in straight rows. The tendency of erosion is to 
break up such cliffs into series of spurs and valleys 









/ 





Fig. 4 — Diagrams Illustrating the Dis- 
location Causing the California 
Earthquake. The Upper Represents 
an Earth Block ioo Feet Square and 
25 Feet Thick, with Indication of 
the Position of the Fracture. The 
Lower Shows the Relation of Its 
Two Parts after Faulting. 



[228] 



Grove Karl Gilbert 

and to obliterate the lakes by cutting down their 
outlets or filling their basins with sediment. Fig. 
2 shows one of the fault-made ponds. This line 
and zone have been recognized by California geol- 
ogists through a distance of several hundred miles. 
It was to this line that attention and expectation 
were especially directed, and it was on this line that 
the surface evidence of new faulting was actually 
found. The new movement was not coextensive 
with the line as previously traced, but affected only 
the northwestern portion; and, on the other hand, 
it extended farther to the northwest and north 
than the old line had previously been recognized. 
The map represents only the line along which 
the recent change occurred. From a point a 
few miles southwest of Hollister it runs north- 
westward in a series of valleys between low 
mountain ridges to the Mussel Rock, ten miles 
south of the Golden Gate. Thence northwestward 
and northward it follows the general coast line, 
alternately traversing land and water. The farthest 
point as yet definitely located is at Point Delgada, 
but the intensity of the shock at the towns of Pe- 
trolia and Ferndale probably indicates the close 
proximity of the fault and warrants the statement 
that its full length is not less than three hundred 
miles. South of Point Arena its course is direct, 
with only gentle flexure, but the data farther north 

[229] 



tf h e California Earthquake of i g o 6 

seem to imply either branching or strong inflexion. 
Opposite San Francisco its position is several miles 
west of the coast line, and it nowhere touches a 
large town. 

That which occurred along this line was a differ- 
ential movement and permanent displacement of 
the rock and earth on the two sides of a vertical 
crack. The principal displacement was not ver- 
tical, but horizontal. If one thinks of the land to 
the east of the crack as stationary, then the change 
may be described as a northward movement of the 
land west of the crack. If the land to the west be 
thought of as stationary then the land to the east- 
ward moved toward the south. It is probable that 
both tracts shared in the movement, the eastern 
shifting toward the south and the western toward 
the north. Perhaps the nature of the change can 
be more readily understood by reference to Fig. 4, 
which represents an ideal block of the earth's crust, 
100 feet square on the surface and 25 feet deep, be- 
fore and after its division and dislocation by the 
earthquake-causing fault. 

Wherever a fence, road, row of trees, or other 
artificial feature following a straight line was inter- 
sected by the fault its separated parts were offset, 
and an opportunity thus afforded for measuring 
the amount of change. The measurements range 
in the main from 6 to 15 feet and have an average 

[230] 




Fig. s — A Faulted Road near the Head of Tomales Bay. The Nearer and More 
Distant Parts of the Road Were Originally in One Line — a Continuous, Straight 
Road. The Present O if set is Twenty Feet. 



K 



I b 



of about 10 feet. At one place (Fig. 5) a road was 
offset 20 feet, but in this case the underlying ground 
was wet alluvium and part of its movement may 
have been due to a flowing of the soft material. 
There was also some 
vertical change, but 
this was not every- 
where in the same 
direction and its 
amount was compara- 
tively small. At many 
points the land west 
of the fault appears to 
have risen one or two 
feet as compared with 
the land at the east. 

The surface mani- 
festation is not usually 
a simple crack, but a 
disturbed zone a few 
feet broad, the earth 
within the zone being 
split into blocks which 
show more or less twisting or rotation. In some 
places the zone is slightly depressed below the ad- 
joining surfaces, and elsewhere slightly elevated. 
Other disturbances of the surface were associated 
with the earthquake, but the track of the central 




Fig. 6 — Ordinary Appearance of the Earth- 
quake Rift Where It Traverses Firm 
Turf. 



[233] 



tf h e California Earthquake of i g o 6 

fault has a character of its own, a character with 
which the field workers soon became familiar, so 
that it could be clearly identified. It came to be 
distinguished in their conversation and note-books 



m 






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'■■"■'- ii 






••' *t v i-'^2iB& r ~ : ^M0M 





Fig. 7 — *4 Zone of Earthquake Fracture Where It Crosses a Road Near Bolinas. 

as "the rift." For considerable distances the rift is 
single, but elsewhere it is more or less divided, 
the parts lying within a few rods of one another 
and being approximately parallel. There are also 
branches parting from the main rift at various 

[234] 




Fig. 8 — Cracks Caused by the Shaking of Marshy Ground. The Comparatively 
Firm Road Embankment Preserved the Cracks Better than the Bog. 



V 



Karl G i I b 



angles and gradually dying out in the adjacent 
country, and in some of these the belt of disturb- 
ance is broad and complicated (Fig. 7). There are 
also outlying cracks occurring within a mile or 
two'of the central rift and having irregular courses, 
and these may probably be referred to the same 
general system of rock strains. 

Other cracks are distinctly secondary in char- 
acter; that is to say, they are not due directly to 
the stresses and strains by which the fault was 
made, but are results of the earthquake itself. The 
jar constituting the earthquake, or in technical 
language the earthquake wave, as it travels through 
rock and earth produces temporary compressions 
and other strains, and these often occasion cracks 
at the surface. Where the material is elastic such 
secondary cracks merely open and close, leaving 
the ground with its original form; but where it is 
inelastic and incoherent, as in the case of young 
alluvial formations and artificial fillings, some of 
the cracks opened by passing waves do not close 
again, but remain as permanent vestiges of the 
shock. Closely associated with these secondary 
cracks in soft ground are permanent changes in 
surface form. At the head of Tomales Bay, for ex- 
ample, a broad tract of soft ground between high 
and low tide was thrown into low ridges, with 
cracks along their crests, and these remained until 

[237] 



tf h e California Earthquake of i g o 6 

destroyed by wind waves. In San Francisco con- 
siderable tracts of "filled" land were shaken to- 
gether and thus made to settle a few feet, and were 
at the same time slidden several feet toward the bay 
(Fig. 9). 

Certain changes, very conspicuous to the observer 
who drove about the country, are closely associated 
with roads. A side-hill road is usually constructed 
by excavating a notch in the natural slope and 
piling the excavated material in an embankment 
at the outer edge of the notch. In course of time, 
and especially during rainy seasons, the embank- 
ment at the outer edge of such a road settles and 
has to be built up as a matter of repair. Portions of 
the bluff on the up-hill side of the notch are also 
apt to fall away, taking the form of small land- 
slides, which have to be removed from the road 
as a rule after every rainy season. The earthquake 
precipitated many changes of this sort. Along all 
side-hill roads in the immediate vicinity of the rift 
a crack was developed between the embankment 
and the original soil against which it rested, and 
this crack often assumed formidable dimensions 
(Fig. 10); in fact its magnitude was found to be a 
convenient index of the local violence of the earth- 
quake in regions where buildings are rare. Land- 
slips from the bluffs margining the roads (Fig. 
11) were also very numerous, in many instances 

[238] 




Fig. 9 — Street Scene in San Francisco, Showing Effect of the Earthquake on 
Filled Ground. — The Distant Part of the Street Probably Retains Its Original 
Level and Position. Nearer by the Ground Has Settled Several Feet and Has 
Also Moved to the Left. 



* 



Grove Karl Gilbert 

stopping traffic until repairs could be made. And 
there were many landslides on a larger scale, the 
earthquake initiating movements which might 
otherwise have been delayed for years or even cen- 
turies. Some of these landslides fell into streams, 
dammed their waters and created temporary lakes. 
• Other disturbances of water supply were more 
directly connected with the earthquake. At several 
points large volumes of water were squeezed from 
the ground during the agitation, causing brief but 
violent torrents, and one of these brought with it so 
much sand as to constitute a sort of sand eruption. 
There are reports also that certain springs have 
received a permanent increase in volume, a result 
which would naturally follow from the modifica- 
tion of underground circulation by the cracking of 
rock and earth. 

Wherever the shock was specially strong there 
was considerable injuries to trees ; some were over- 
turned, others broken near the ground, and yet 
others broken near their tops. A number of large 
redwood trees standing on the line of the rift were 
split from the ground upward, the basal portions 
being faulted along with the ground they stood on. 

In the systematic survey of the earthquake area 
the relative intensity is being estimated by means 
of the records of various physical effects. In the 
immediate vicinity of the fault road-cracks and 

[241] 



°T k e California 'Earthquake of i g o 6 

cracks in alluvium are large and numerous; many 
trees were broken or overturned; there were many 
landslides ; half of the wooden buildings of any vil- 
lage or hamlet were shifted horizontally, often 
with serious injury; buildings and chimneys of 
brick or stone were thrown down; during the 
shock men, cows, and horses found it impossible to 
stand, and fell to the ground; and some persons 
were even thrown from their beds. In a general 
way all these evidences of violence diminish gradu- 
ally with distance from the fault on either side. The 
rate of diminution, with exceptions to be mentioned 
presently, may be expressed by saying that at five 
miles from the fault only a few men and animals 
were shaken from their feet, only a few wooden 
houses were moved from their foundations, about 
half the brick chimneys remained sound and in con- 
dition for use, sound trees were not broken, and 
no cracks were opened which did not immediately 
close. At a distance of twenty miles only an occa- 
sional chimney was overturned, the walls of some 
brick buildings were cracked, and wooden build- 
ings escaped without injury; the ground was not 
cracked, landslides were rare, and not all sleepers 
were wakened. At seventy-five ■ miles the shock 
was observed by nearly all persons awake at the 
time, but there were no destructive effects; and at 
two hundred miles it was perceived by only a few 
persons. 

[242] 




Fig. io- — Road Crack Caused by the Earthquake. 



Grove Karl Gilbert 

A number of exceptions to this gradation of in- 
tensity are connected with tracts of deep alluvial 
soil, especially if saturated with water, and with 
tracts of "made ground. " The great destruction in 
the low-lying part of San Francisco, eight miles 
from the fault, is directly connected with the fact 
that much of the ground there is artificial, the area 
having been reclaimed from the bay by filling in 
with sand and other materials. The severity of the 
disaster at San Jose, twelve miles from the fault, 
has been ascribed to the deep alluvial soil 
on which the town stands, and many other 
local peculiarities seem to admit of the 
same explanation. It is necessary also to 
distinguish carefully between earthquake intensity 
and destructive effect, because injury to property 
was conditioned by mode and material of construc- 
tion no less than by intensity of vibration. But 
after making due allowance for differences in nat- 
ural foundation and for differences in the resisting 
power of buildings, there remain various anomalies 
for which satisfactory explanation has not as yet 
been found. The natural foundation of Oakland 
is similar to that of San Jose, and its distance from 
the earthquake origin is about the same, but the 
injury to its buildings was decidedly less; and Santa 
Rosa, standing on ground apparently firmer than 
that at Oakland or San Jose and having a some- 

[245] 



T h e California Earthquake of i g o 6 

what greater distance from the fault, was never- 
theless shaken with extreme violence. 

It is too early to discuss these anomalies. With 
the data now in hand it seems to be true that there 
are outlying tracts of high intensity surrounded 
by areas of relatively low intensity; and these 
features, if they shall be fully established, will 
doubtless affect in some important way the general 
theory of the earthquake. 

One of the chief uses of time observations in 
connection with most earthquakes has been to de- 
termine the position of the origin. As the elastic 
wave travels outward in all directions from the 
initial point it reaches successively points on the 
earth's surface which are more and more remote. 
Coseismal lines, or lines of simultaneous arrival, 
are, therefore, closed curves circling about the 
region of the initial fracture. In the case of the 
California earthquake this particular function 
of the coseismals is not required, because the frac- 
ture is visible at the surface; but they are not there- 
fore without value. It is not to be supposed that 
the yielding of the earth occurred at the same 
instant throughout the entire extent of the fault 
plane. We should assume, rather, that the fracture, 
beginning at some point, was extended thence to 
the remainder of the tract, a certain amount of 
time being consumed in its propagation. When 

[246] 




Fig. ti — Small Landslide on the Uphill Side of a Side-Hill Road. 



V 



K a 



1 



I b 



the time data have been collected and studied, it 
may be possible to determine at what point the 
fracture began and at what rate it was extended. 
It is hoped also that when the time records and 




Fig. 12 — Water Tank Thrown from Its Pedestal by the Earthquake. 

intensity records shall have been systematically 
discussed there may result some conclusion as to 
the depth to which the fault extended and also as 
to its subterranean form. 

Mention has already been made of the question 
whether the permanent dislocation or change of 

[249] 






°T k e California Earthquake of i g o 6 



absolute position involved in the faulting was 
divided between the tracts of land on the two sides 
or was confined to one or the other of them. At 
first sight it would appear that the only thing 




Fig. 13 — School-House at Point Reyes Station, Near Inverness; Shifted Horizontally 
Two and One-Half Feet by the Earthquake. The Corner Here Shown Was 
Slipped from the Foundation and Rests Directly on the Ground. 

susceptible of actual determination is the relative 
displacement, and that the absolute displacement, 
or the real movement with reference to the earth 
as a whole, must remain a matter of theory only. 
Nevertheless, it happens that in this particular 
instance the real changes in geographic position 
are not only susceptible of determination, but are 

[250] 



V 



K a 



I 



I b 



actually to be investigated. To illustrate the prob- 
lem, let XT represent, in ground plan, a portion of 
the fault line, and let ABB'C be the original posi- 
tion of a straight line intersected by the fault. 
Assuming for the moment that the dislocation was 
equal on the two sides of the fault, then the line 
AB was carried to the 
position DE, and the 
line B'C to the position 
FG. We may think of 
the distances BE and 
B'F as each equal to 
five feet. The disloca- 
tion of five feet per- 
tains to every point 
near the fault line, but 
it is not supposable 
that the same disloca- 
tion affects points at a 
great distance from the 
fault. At some remote 

point, for example Z, in the direction B'C, there 
was no displacement. If B'C and FG were 
both produced in that direction they would be 
found not precisely parallel, but would eventu- 
ally coalesce. How far the undisturbed region 
Z may be from the fault line is a matter of 
pure conjecture, but we may plausibly assume that 




Fig. 14 — Diagrammatic Plan of a Portion 
of the Earthquake Fault, Illustrating 
Changes in Geographic Position. 



[251] 



*¥ h e California Earthquake of i g o 6 

the transverse dimension of the area affected by 
the displacement is of the same order or magnitude 
as the length of the fault line and is measured by. 
hundreds of miles. If this assumption is correct, 
then throughout a great region in central and 
northern California all points have experienced a 
change in geographic position, the change in the 
vicinity of the fault being of about five feet and 
the amount diminishing toward the northeast and 
southwest. If the only determinations of latitude 
and longitude within this area were of the ordinary 
approximate character, it would be impossible to 
measure the changes in geographic position the- 
oretically accomplished by the fault; but it for- 
tunately happens that the region is traversed by 
two belts of the triangulation of the United States 
Coast and Geodetic Survey, one being a system of 
triangles for the control of the coastal map work, 
and the other the elaborately measured transcon- 
tinental belt. The region thus contains several 
scores of points whose co-ordinates have been de- 
termined with a high degree of precision, and it is 
possible by the redetermination of these positions 
to measure the dislocations which have taken place 
in connection with the earthquake. As all topo- 
graphic and hydrographic maps of California 
are dependent for their latitudes and longitudes 
upon the positions given by this triangulation, and 

[252] 



Grove Karl Gilbert 

as there is reason to believe that many of these 
positions have been disturbed by a measureable 
amount, the superintendent of the Coast Survey 
has determined to repeat so much of the work of 
triangulation as may be necessary in order to re- 
determine the geographic positions. And it is 
proposed to carty this work far enough eastward 
to connect the redetermined points with stations 
that may safely be regarded as quite beyond the 
effect of the recent fault. When this has been ac- 
complished much light will be thrown on the 
nature and distribution of the strains which were 
relieved by the dislocation along the fault line, and 
it will be possible to say definitely whether the 
original displacement involved the territory on both 
sides of the fault or on one side only. 

A further check is to be afforded through the 
observations for astronomic latitude at Ukiah. The 
observatory at Ukiah is between 25 and 30 miles 
in a direct line northeast of the fault. In connec- 
tion with the general dislocation it was presumably 
moved toward the southeast and its latitude 
diminished by several hundredths of a second. This 
is one of an international series of observatories 
established in approximately the same latitude but 
in different longitudes, for the purpose of determin- 
ing variations in the position of the earth's axis of 
rotation. If the observations at Ukiah were 

[253] 



The California Earthquake of i g o 6 

studied alone it might not be possible to separate 
the result of a small change in the observatory's 
position from the effects of the migration of the 
axis; but by combining the Ukiah data with those 
furnished by the other observatories of the system, 
it is probable that the effects of the two causes can 
be discriminated. 

The most important practical results of the 
various earthquake studies will probably be af- 
forded by the engineers and architects, and will 
lead to the construction of safer buildings in all 
parts of the country specially liable to earthquakes; 
but the geologic studies of the State Commission 
are not devoid of economic bearings. In the city 
of San Francisco and adjacent parts of the penin- 
sula on which it stands the underlying formations 
include several distinct types, and the district is so 
generally occupied by buildings that the relations 
of the several formations to earthquake injury can 
readily be studied. Such a study is being made 
with care and thoroughness, and one of its results 
will be a map of the city showing the relation of 
the isoseismals, or lines marking grades of inten- 
sity, to tracts of solid rock, to tracts of dune sand 
in its natural position, to upland hollows partially 
filled by grading, and to old swamps, lagoons and 
tidal marshes that have been converted into dry 
land by extensive artificial deposits. The informa- 

[254] 



Grove Karl Gilbert 

tion contained in such a map should guide the re- 
construction and future expansion of the city, not 
by determining the avoidance of unfavorable sites, 
but by showing in what areas exceptional precau- 
tions are needed, and what areas demand only 
ordinary precautions. 

Another economic subject to which the commis- 
sion may be expected to give attention is what 
might be called the earthquake outlook. Must the 
citizens of San Francisco and the bay district face 
the danger of experiencing within a few genera- 
tions a shock equal to or even greater than the one 
to which they have just been subjected? Or have 
they earned by their recent calamity a long im- 
munity from violent disturbance? If these ques- 
tions could be answered in an authoritative way, 
or if a forecast could be made with a fair degree 
of probability, much good might result; and even 
if nothing more shall be possible than a cautious 
discussion of the data, I believe such a discussion 
should be undertaken and published. Of snap 
judgments there has been no lack, and the Califor- 
nia press has catered to a natural desire of the 
commercial public for an optimistic view; but no 
opinion has yet been fortified by an adequate state- 
ment of the pertinent facts. Among these facts 
are the distribution of earthquake shocks as to 
locality, time and severity in California, and also 

[ 255 ] 



tf h e California Earthquake of i g o 6 

in the well-studied earthquake district of Japan; 
the relation of the slipping that has just occurred 
to the geologic structure of the coast region; the 
relation of other fault lines to the bay district; and 
the relation of the recent shock to a destructive 
shock that occurred in 1868. If a broad and candid 
review of the facts shall give warrant for a fore- 
cast of practical immunity, the deep-rooted anxiety 
of the community will find therein a measure of 
relief. If a forecast of immunity shall not be war- 
ranted, the public should have the benefit of that 
information, to the end that it shall fully heed the 
counsel of those who maintain that the new city 
should be earthquake-proof. In any case, timidity 
will cause some to remove from the shaken district 
and will deter others who were contemplating im- 
migration; but such considerations have only tem- 
porary influence and can not check in an important 
way the growth of the city. The destiny of San 
Francisco depends on the capacity and security of 
its harbor, on the wealth of the country behind it, 
and on its geographic relation to the commerce 
of the Pacific. Whatever the earthquake danger 
may be, it is a thing to be dealt with on the ground 
by skilful engineering, not avoided by flight; and 
the proper basis for all protective measures is the 
fullest possible information as to the extent and 
character of the danger. 

I 256] 



Local Effects of the California 
Earthquake of 1906 



By 

Stephen Taber 

Stanford University 



Local Effects of the California 
Earthquake of 1906 



THE principal damage done by the California 
earthquake of April 18, 1906, was con- 
fined to a long, narrow area extending 
along the Pacific coast in a northwest-and-southeast 
direction, with the city of San Francisco near its 
center. The area in which the greatest damage was 
done is a little over 200 miles in length and scarcely 
40 miles in width. The earthquake may be ac- 
counted for by the geological structure. The prin- 
cipal valleys of California have been formed by a 
system of parallel faults running in a general north- 
west-and-southeast direction, and the disturbance 
occurred along one of these old fault-lines. 

The particular fault which caused the earth- 
quake is the Stevens Creek (Portola-Tomales) 
fault; it has been traced across the Santa Cruz 
quadrangle by Dr. J. C. Branner and Dr. J. F. 
Newsom, and is described by them in the un- 
published Santa Cruz folio of the United States 
Geological Survey. It runs from Crystal Springs 
Lake through Woodside and the Portola Valley, 
over the saddle that joins Black Mountain with the 
crest of the Santa Cruz Range, down the Stevens 

[259] 



tf h e California Earthquake of i g o 6 

Creek Canon, crosses Campbell Creek about 2 
miles southwest of Saratoga and continues in the 
same southeasterly direction toward Loma Prieta. 
From Crystal Springs Lake the fault has been 
traced toward the northwest by Professor A. ,C. 
Lawson through San Andreas Lake and out into 
the ocean near Mussel Rock, about 7 miles south 
of the Cliff House at San Francisco. 

The topography indicates that the fault-line 
continues its northwesterly course through Bolinas 
Bay and Tomales Bay, and that it finally leaves 
the coast near Point Arena in Mendocino County. 

The present paper deals only with the move- 
ments that took place along this fault-line between 
Crystal Springs Lake and Black Mountain, and 
with the effects of the earthquake on the district 
lying on both sides of the fault-line and extending 
from San Francisco Bay to the Pacific Ocean. 

The Stevens Creek fault is one of the most 
recent, for it cuts gravel beds that were laid down 
as late as the Pliocene or perhaps Pleistocene 
period. The old uplift along the Stevens Creek 
fault is on the northeast side, and the rocks on both 
sides of the fault dip in a northeasterly direction. 
The Miocene sandstones that form the greater part 
of the Santa Cruz Range come down to the fault- 
line on the west, but on the east side erosion has 
removed the overlying beds and exposed the 

[260] 




Map of the Stevens Creek 
Scale of Miles 



o s to to 30 40 



Fig. i. 



s 



<t 



Franciscan series, so that it is only at some distance 
away from the fault toward the east that the Mio- 
cene sandstones and gravels reappear. 




Fig. 2. 

At about fifteen minutes after five o'clock on 
the morning of April 18, 1906, the Stevens Creek 
fault was suddenly refractured, and a new displace- 
ment occurred along the old fault-line, producing 
the earthquake that shook the adjacent region. 

[263] 



°T k e California Earthquake of i g o 6 

This new displacement is chiefly lateral, the 
southwest side of the fault having moved toward 
the northwest, or vice versa; and in some places 
this has been accompanied by a small uplift on the. 



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Fig. 3— Road Crossing the Fault Line Two Miles Southeast of Portola. There Is 
a Vertical Uplift on the Northeast Side of the Fracture at This Place. 

northeast, or a small downthrow on the southwest, 
or both. The lateral displacement is well defined, 
as far as it has been traced, and at some points 
amounts to as much as 9 feet. The vertical dis- 
placement in most places is not so evident, but 
about a mile southeast of Portola there is an uplift 

[264] 






Stephen 7 a b e r 

of 2 feet on the northeast side, and the same 
amount of vertical displacement has been observed 
on Black Mountain. 

The valleys through which the old Stevens Creek 







Fig. 4 — Showing a Fence That Crossed the Fault at an Oblique 
Angle. The Post Shown in the Photograph Was Split and 
Pulled Apart and tlte Wires Broken. 

fault runs are filled with silt and gravels, so that it 
is impossible to get at bed-rock along the fault line, 
but it is probable that the rocks along this line 
have been so broken and crushed by past move- 

[265] 



tf h e California Earthquake of i g o 6 

ments that they would offer little or no additional 

information in regard to the recent displacement. 

Through the Portola Valley, and for about 3 

miles northwest of Woodside, the fracture runs 




Fig. 5 — Showing a Fence That Was Broken and if set Eight Feet Where It 
Crossed the Fracture. 

in a continuous and almost straight line. At a little 
distance it looks as though a furrow had been run 
down the valley with a big plow. In places the 
earth has been piled up into ridges 2 or 3 feet high, 
and at other places fissures have been opened that 
measure 2 T / 2 feet in width. Two and a half miles 
southeast of Portola the fissure is 3 feet across. 

\266^ 



p 



T 



The ground is usually cracked and broken for a 
distance of 10 or IS feet on both sides of the main 
fracture, which in places splits up into numerous 
minor cracks. 




Fig. 6 — Photograph of a Fence Crossing the Fault-Line at Right 
Angles. The Man is Holding an Eight-Foot Transit Rod and 
Stands in Line with Continuation of the Fence on the Far Side 
of the Fracture. The Fence Was Repaired Before the Photo- 
graph Was Taken. 

Two miles southeast of Crystal Springs Lake the 
resistance to displacement appears to have been 
greater, and, instead of slipping along a straight 
line, the ground has been broken into a belt of 

[267] 



tf h e California Earthquake of i g o 6 

parallel, north-and-south, shearing cracks, running 
at an angle of approximately 45° with the general 
movement. Some of these shearing cracks are from 
\y 2 to2 feet wide, and the belt of cracks extends for 
a quarter of a mile or more. 

Black Mountain was badly shattered, and there 
are numerous cracks running over it in all direc- 
tions. Fences crossing the fracture are broken; 
those that run in a north-and-south direction have 
their boards bent into arches or crushed, and the 
ends shoved past each other, while those that cross 
in a northwest-and-southeast direction have been 
pulled apart, and wire fences have been broken by 
tension. Fences that cross the fracture at right 
angles have been broken and displaced 8 or 9 feet. 

The photograph (Fig. 6) shows a line fence 
crossing the fault a mile southeast of Woodside. 
This fence was broken and displaced over 8 feet, 
but had been repaired before the photograph was 
taken. The man at the right in the picture is hold- 
ing an 8-foot transit rod, and he is standing in line 
with the continuation of the fence on the far side 
of the fracture. The crack crosses the fence just 
back of where he is standing. 

A striking evidence of displacement is shown in 
the earth dam that divides the Crystal Springs 
Lake. This dam is about 500 feet in length, and 
the road from San Mateo to Half Moon Bay runs 

[ 268 ] 




Fig. 7 — Dam at Crystal Springs Lake, Showing Cracks 
Formed by the Displacement. 



s 



along its crest. The accompanying sketch (Fig. 
7) shows the position and direction of the cracks 
that were formed in the dam. The larger cracks 
are about 6 inches wide and are parallel with the 







«3asssr 

..-•■ -..--■ : • * . ■ 

"' '■' ' ' V * " ' * 4 > 





Fig. 8 — -/4ra Oak Tree Six Feet in Diameter Uprooted by the Earthquake Three 
Hundred Yards from the Fault Line. 

dam. Smaller intersecting cracks were formed 
near the northeast end of the dam along the prob- 
able line of the fault, and the road was offset about 
6 feet at this point. The fences on both sides of the 
road were broken in a number of places, and the 
unbroken boards were bent and arched so as to give 

[271 ] 



tf k e California Earthquake of i g o 6 

a serpentine appearance to the fences. The wires 
of a telephone line crossing the dam sag in great 
loops. 

It seems probable that the total displacement is 
greater than the amount that may be directly meas- 
ured at any place along the line of the fracture, for 
there is evidence of drag in the soil for a consid- 
erable distance on both sides. Water-pipes at a 
distance of several hundred feet from the fault-line 
have been pulled apart, telescoped, or bent in the 
direction of the movement, and fences formerly 
straight have been bent into a slight curve for a 
distance of 200 or 300 yards from the fracture. 

The intensity of the shock was greatest along the 
line of faulting and decreases as one goes away 
from this line. In comparing the intensity of the 
shock at different places, the best evidence was sup- 
plied by the oak trees broken and uprooted where 
the intensity was greatest, by the percentage of 
country water-tanks thrown down, and, as the 
intensity decreased, by the condition of plastering 
in houses and the number of brick chimneys found 
standing. 

There are many white oaks (Quercus lob at a) 
growing in the valleys through this section of the 
country, and in a belt extending for not more than 
400 or 500 yards on each side of the fracture many 
of these trees have been uprooted or have had large 

[272] 



? 



branches whipped off. Sound limbs 2 feet thick 
were broken off by the shock, and there are trees 
having a diameter of more than 6 feet that were 
overturned during the earthquake. About 300 
yards southwest of Searsville Lake a live oak 
(Quercus agri folia), growing within a few feet of 
the fracture, was split down the trunk by the 
violence of the movement, but is still standing. 

On Cahill Ridge, 2 miles southwest of the fault- 
line,, there are redwoods (Sequoia semperdrens) 
that had their tops snapped of! 75 or 100 feet above 
the ground. The intensity of the shock was much 
less at this point than near the line of fracture, but 
the redwood is brittle compared with the oak. 

Frame houses, strongly built and having good 
foundations, stood the shock well, even when close 
to the fault-line, but brick and stone structures 
were badly damaged at distances of more than 12 
miles from the fracture. Fortunately for the in- 
habitants, most of the houses near the fault-line 
were one-story frame buildings. 

Most of the water-tanks that stood within 3 or 
4 miles of the fracture were thrown down, but 
farther away the percentage of tanks that are 
standing gradually increases. With but few ex- 
ceptions, all brick chimneys within 3 or 4 miles of 
the fault-line were thrown down, but at a distance 



273 



tf h e California Earthquake of i g o 6 

of 8 or 9 miles probably more than 50 per cent are 
still standing. 

Within the area under discussion the earthquake 
seems to have consisted of two separate and dis- 
tinct kinds of movement: one a violent vibration 
in a northwest-and-southeast direction, parallel to 
the fracture, and probably caused by the sudden 
displacement; the other a wave-motion, traveling 
at right angles to the fracture and generated by 
the rocks slipping past each other along the fault- 
line. 

It was the first motion that snapped off branches, 
overturned oak trees and wrecked buildings in the 
immediate vicinity of the fault-line; and although 
this motion extended for a considerable distance, 
the damage it caused was limited to a belt not over 
a mile distant from the fracture. 

The following facts appear to bear out the the- 
ory of a violent initial movement parallel to, the 
fault-line. Most of the trees that were overturned 
fell toward the northwest or southeast, and the 
buildings that were destroyed near the line of frac- 
ture tended to move in the same direction; but 
frame buildings do not furnish very reliable data. 
Beds and furniture rolled back and forth in direc- 
tions parallel to the vibration. The strongest evi- 
dence is furnished by the movements of liquids, 
such as milk and water. In the immediate vicinity 

[274] 



p 



of the fracture many places were found where the 
water had splashed out of reservoirs and tanks on 
the northwest and southeast sides, and at one place 
the motion had been so violent that the water in 
a large wooden tank had splashed against a roof 
placed over it with sufficient force to drive shingles 
from the northwest side. In some places large 
water-tanks holding 3,000 or 4,000 gallons were 
almost emptied by the splashing. 

The wave-motion was responsible for most of 
the damage done outside of the narrow belt along 
the line of fracture. Several people, who were out 
of doors at the time of the earthquake and several 
miles from the fault-line, state that the ground 
appeared to move like the waves of the sea. While 
these statements cannot be used as conclusive evi- 
dence, there are many facts that indicate a true 
wave-motion, having distinct crests. Water in 
reservoirs and tanks, standing at a distance of 
several miles from the fault-line, splashed out on 
the northeast and southwest sides. At King's 
Mountain House, a little over 2 miles southwest of 
the fracture, there were a number of milk-pans 
setting on shelves. All of the cream went out on 
the southwest side of the pans, and afterward the 
milk splashed back and forth, spilling out on both 
the southwest and northeast sides. At a barn 3 
miles northeast of Woodside, heavy carriages 



[275] 



the California Earthquake of i g o 6 

standing with their wheels parallel to the fault-line 
were moved sideways a distance of 6 inches, but 
did not roll forward on their wheels. 

At Stanford University, Ay 2 miles northeast of 
the fault-line, the sandstone buildings afford evi- 
dence of the wave-motion. Walls running north- 
west and southeast, when free to fall, fell by top- 
pling over, and the stones lie on the ground in 
nearly the same relative positions that they occu- 
pied while standing. Walls running more nearly 
parallel to the direction of wave-motion were 
crushed, and the stones fell in irregular piles, while 
the walls that are still standing show 45° shearing 
cracks. Perhaps the best evidence of a true wave- 
motion is to be found in the arches. When the 
crest of a wave struck an arch running northeast 
and southwest, the arch was pulled apart, allowing 
the keystones to drop a short distance. There are 
forty-six arches running approximately northeast 
and southwest in which the keystones dropped, 
while only twelve arches running northwest and 
southeast had their keystones lowered, and some of 
the latter may be accounted for by the falling of 
neighboring walls. It might be well to state that 
there were more arches running northwest and 
southeast than at right angles to that direction. 
Most of the keystones dropped only 5 or 6 inches, 
but some fell out completely. 

[276] 



s 



There are several strongly built, low, one-story 
frame houses, of the bungalow type, standing 
within a few hundred feet of the fault, which 




Fig. 9 — Photograph of Arches at Stanford University, 
Showing Keystones Lowered During the Earthquake. 
These Arches Were Nearly at Riglit Angles to the 
Fault-Line. 

scarcely had their plaster cracked, excepting where 
chimneys fell through. Broken oak trees growing 
close to these houses indicate the intensity of the 
shock. This suggests that the wave-motion, with 
its shearing action, was more damaging to walls 

[277] 



tf h e California Earthquake of igo6 

than a back-and-forth vibration. Another inter- 
esting fact in this connection is that most two- 
story frame buildings at a distance of 5 or 6 miles 
from the fault-line did not have the plaster cracked 
on the second floor, although the plaster on the 
first floor was usually badly cracked and broken. 

Brick buildings at a distance of 10 miles from 
the fault-line showed the effects of a wave-motion. 
At Guth Landing, on San Francisco Bay, 9 J / 2 miles 
northeast of the fracture, there was a large brick 
warehouse, with its ends parallel to the fault-line. 
The upper half of each end toppled over, but the 
side walls, although badly cracked, were left 
standing. 

The effects of this wave-motion have not been 
traced more than 12 miles from the fault-line, but 
it probably continued with diminished intensity to 
a considerable distance. In other districts, having 
a different geological structure, the distances to 
which these movements could be traced would un- 
doubtedly vary greatly. The wave-motion appears 
to have been more intense in the soft alluvial de- 
posits of the valleys than in the consolidated beds 
that form the high ground, but there are not enough 
houses in the mountains of this district to furnish 
conclusive evidence on this point. 

At Half Moon Bay the intensity of the earth- 
quake was about the same as at Stanford Univer- 

[278] 



f 



sity; but as one goes down the coast, and therefore 
away from the fault-line, the intensity decreases. 
At Pescadero, which is about 12 miles from the 
fault-line, there was scarcely any damage done, but 
there were no brick or stone buildings in that 
village. 

In regard to the geological effects of the earth- 
quake, there are a few facts of general interest that 
might be mentioned. Most of the landslides that 
occurred at this time were on the west side of the 
Santa Cruz Range. This is probably to be attrib- 
uted to the greater rainfall on that side of the water- 
shed. The springs and streams on both sides of the 
range increased in volume after the earthquake, and 
some creeks on the west side were nearly doubled. 
All of the streams were muddy for several days 
after the earthquake. 

A marked effect was produced on the artesian 
belt near the head of San Francisco Bay. Wells 
that had previously been dry began flowing, and 
wells that flowed before the shock greatly increased 
in volume and pressure. The following is one illus- 
tration out of many that were recorded: A well 
near Alviso, at the head of the bay, formerly re- 
quired a wind-mill to pump the water. At the time 
of the earthquake the casing was driven 2 feet 
out of the ground, wrecking the pump, and since 
that time the well has been flowing under a heavy 

[279] 



^ h e California Earthquake of i g o 6 

pressure. In some of the lowlands small cracks 
formed, out of which water issued, bringing up 
mud and sand. 



280 






Preliminary Note on the Cause of 
the California Earthquake of 1906 

By 

F. Omori, Sc.D. 

Member of the Imperial Earthquake Investigation Committee 
Tokyo, Japan 



The Cause of the California Earth- 
quake of April 18, 1906 

By F. Omori, Sc.D. 



/. Introduction. The great earthquake of April 
18, 1906, which caused an enormous amount of 
damage in San Francisco, furnished a rare oppor- 
tunity of studying the different earthquake phe- 
nomena, especially the seismic effects on various 
modern structures. Immediately upon receipt of 
the news of the catastrophe, the Imperial Govern- 
ment resolved to dispatch to California Professors 
T. Nakamura and T. Sano, and myself, for the pur- 
pose of making investigations on the great seismic 
disturbance, each according to his professional 
point of view. The party departed from Tokyo on 
May 1st, and arrived at San Francisco on the 18th 
of the same month, the present writer remaining 
about eighty days in California. 

My special thanks are due to Professor George 
Davidson, and also to Professors Lawson and 
Leuschner of the University of California, Dr. Gil- 
bert, of the U. S. Geological Survey, Mr. K. Uyeno, 
Japanese Consul, and other American and Japan- 
ese gentlemen, with whom I came in contact and 

[283] 



tf h e California Earthquake of i g o 6 

who gave me most cordial assistance during my 
stay in California. 

2. tfime of Occurrence. The times of earth- 
quake occurrence observed at the California Univer- 
sity and the Lick Observatory were respectively 
5 h 12 m 39 s and 5 h \2 m \2 S A.M. (Western States 
Time, or that of longitude 120° W.); the time of 
commencement of the disturbance at the origin 
itself being probably about S h 12 w A.M. 

j. Area of Destructive Motion. The area, with- 
in which more or less damage was done, was very 
long, extending over a distance of 550 miles along 
the Pacific coast, from the vicinity of Salinas on 
the south to the vicinity of Eureka on the north. 
The width or extent from the coast of the strong- 
motion area is probably some fifty miles. The 
earthquake of April 18th was thus greater, in 
length, than the large Japan earthquake of 1891, 
the length of whose area of strong motion was 
about 400 miles. The intensity of motion in the 
California earthquake was, however, less violent 
than in the other, and the amount of the cas- 
ualties in San Francisco and the different parts of 
the strongly shaken zone was small comparatively. 

4. Sea Waves. When an earthquake of inland 
origin is large and violent, the waters of ponds, 
rivers or lakes are more or less disturbed. So simi- 
larly a great submarine earthquake is often fol- 

[ 284 ] 



F . O m o r i , S c . D . 

lowed by tidal waves ; the time interval between 
the occurrence of the earthquake shock and the 
arrival of the destructive sea waves varies from a 
few minutes to several hours, and depends on the 
distance of the origin from the shore. Tidal waves 
which are not to be noticed on high seas are de- 
veloped most markedly in bays with shallow waters 
and an open mouth, but are quite insignificant 
along deep-water straight coasts. Many of the 
great earthquakes originating off the Pacific coast 
of Alaska and Central and South America have 
been accompanied by large tidal waves. But fortu- 
nately, this phenomenon which sometimes causes 
more damage than the earthquake disturbances it- 
self was so far not very destructive along the coast 
of the United States. The great earthquake of 
April 18th last produced distinct, but very small, 
disturbances of the bay waters which were clearly 
recorded on the tide gauge at the Presidio (San 
Francisco) ; the amount of the rise and fall of the 
sea water being only about 6 inches, repeated in 
about 40 minutes. Now the wave period or periods 
at a place on a given coast remain constant in all 
the tidal waves, irrespective of the origin or cause; 
a destructive tidal wave consisting simply in the 
increase of the amount of the water motion existing 
more or less at all times, in consequence of a strong 
submarine earthquake or eruption, a storm, or some 

f28 5 l 



T* h e California Earthquake of i g o 6 

other agency. A seismic tidal wave is caused by 
the movements communicated from the sea bottom 
to the superincumbent water mass: a very big 
water disturbance taking place when the earth- 
quake focus is at the sea bottom itself or at a very 
small depth below it, accompanied by some changes 
in the contour of the sea bottom. The absence of 
any great tidal disturbance on April 18th shows 
that there was no great submarine depression or 
vertical dislocation, although it seems probable 
that the northern half of the epifocal zone was 
under the Pacific. 

5. Sea Shock. The steamer "Argo" felt the 
earthquake shock on sea near Cape Mendocino, the 
sensation being like that caused by running 
aground. There were other vessels which experi- 
enced the earthquake in a similar manner. 

Effects like these, which may be called "sea- 
shocks," are due to the direct transmission through 
water of vibratory earthquake movements, and not 
due to the phenomena of the tidal waves which are 
developed only along coasts where there is some 
indentation. 

6. Approximate Position of the Center of Epifocal 
Zone. A rough idea as to the position of the most 
central or principal point in the zone, which forms 
the origin of the earthquake, may be obtained from 
a good seismograph record taken at the Lick 

[286] 



PL. I. 




Fig. i. San Francisco and the Vicinity, Showing the Course of the Great 
Fault, from Pt. Arena to Chittenden. 



F . O m o r i , S c . D . 

Observatory, where the preliminary tremor lasted 
about 10 or 12 seconds, from which it may be cal- 
culated that the distance between the point in ques- 
tion and Mt. Hamilton was about 80 or 90 miles; 
the predominating direction of motion there being 
NNW and SSE. These data indicate a place near 
the Tomales Bay as the most central point of the 
disturbance. The approximate position of the lat- 
ter may be assumed to be at a point, latitude 
38° 15'N, longitude 123° W. 

7. tfhe Epifocal Zone. One of the peculiar fea- 
tures in the topography of the State of California 
is a straight depression whose direction is NNW 
and SSE and which extends through the valley of 
the Gualala River, and Tomales and Bolinas Bays, 
continued further southeastwards for some dis- 
tance. This depression, which must have been 
formed in bygone ages by a great sudden convul- 
sion of the earth's crust, or by the gradual moun- 
tain-making force going along the Pacific Coast, 
shows signs of dislocations caused at no very re- 
mote epoch by some great earthquakes, and it is 
of a special interest that the earthquake of April 
18th again produced along the same old weak zone 
a continuous series of remarkable surface manifes- 
tations of cracks, depression, or horizontal slipping, 
constituting what is called a "fault" in geology. 
This fault which has been most carefully studied 

[289] 



tf h e California 'Earthquake of i g o 6 

by Dr. Gilbert of the U. S. Geological Survey, Pro- 
fessors Lawson and Branner, and other able 
geologists of the California and Stanford Universi- 
ties, begins on the north at the right-hand mouth 
of the Alder Creek, near Pt. Arena, and passes into 
the ocean at the vicinity of Fort Ross; it again ap- 
pears at the Bodega Head and at the eastern side 
of the mouth of Tomales Bay, crosses to Inverness, 
on the west shore of the same bay, and then passes 
through the vicinity of Pt. Reyes Station, con- 
tinued to a place about 4 miles to the west of the 
Stanford University; marked disturbances of the 
ground being also distinctly shown to the south- 
east, in the vicinity of Wrights and Chittenden. 
The length of the visible fault is thus over 150 
miles, being three times that of the fault line in the 
great Japan earthquake of 1891. It is, further, 
extremely probable that the northwestern part of 
the present fault is continued beyond Pt. Arena 
under the ocean some 120 miles more and extends 
to the vicinity of Cape Fortuna. That the fault 
was not a mere surface phenomenon is shown by 
the appearance of the same disturbance across the 
tunnel near Wrights Station, at a depth of some 700 
feet below the mountain surface. See Fig. 1 (PI. 
I) and Fig. 2 (PL II). 

8. Shear of the Ground. The shearing movement 
of the ground produced many remarkable results; 

[290] 



aiiiii 





9 



3 1 

o § 

IS 

f J 

f f 

! 

§ 

S 







m 



D 



roads, fences, and every other thing crossed by the 
line of disturbance being cut apart and displaced 
considerably. There were cases in which even 
large redwood trees were split by the shearing 
motion of the ground. 

Fig. 4 relates to the shear effect observed near 
Olima, a village situated between the Tomales and 
Bolinas Bays. The fault passed just in front of a 
house (Skinner's Ranch) and produced a relative 
displacement of 16 feet, a 
garden walk being carried 
through that distance from 
a to b. 

Fig. 11 (PL III) shows 
the shearing effects on a 
pier at Inverness, on the 
west coast of the Tomales 
Bay. The end part of the pier was separated 
from the rest and was displaced about 20 feet 
toward NNW. The direction of displacement 
in this particular instance was opposite to the 
general direction of the relative slip along the great 
fault line. 

Fig. 12 (PL III) shows one of the fault cracks 
produced among the hills above Fort Ross. It will 
be observed that the new disturbances appeared 
along a depression marked by a series of small 
ponds (shown at the right-hand side of the cut), 




Fig. i. 



[293] 



tf h e California Earthquake of i g o 6 

these latter being traces left by a former great 
earthquake. 

Fig. 13 shows the remarkable compression and 
shear effects along one of the parallel fault cracks, 
observed on elevated grounds near the town of 
Manchester, not far from Pt. Arena. A foot-scale 
placed in the foreground will show the size of the 
overlapping earth pieces, whose plan is given in 
Fig. 8. 

g. Remarks on Shearing Movements. For the sake 
of illustration, let us first consider cracks of a wall 
when the earthquake motion is parallel to the 
latter. 

Let abed (Fig. 5) be a 
f wall whose bottom side a b 
is fixed, either absolutely or 
relatively, while the upper 
F*. $ side c d is brought to the 

position c d' as the result of a shearing stress in the 
direction of a to b. Then the rate of the length 
change of the line a e y connecting a with any point 
e on the side c d, will be greatest when the angle 
d a e is equal to 45°. Consequently there will be 
formed a series of cracks at right angles to the lines 
of greatest elongation and at an angle of 45° to the 
base a b. 

Thus, in the case of a strong horizontal motion 
parallel to the plane of the wall, there will be two 




[294] 







m 



D 




Fig. 6. 



sets of cracks at right angles to one another, as in 

Fig. 6. 

Fig. 14 (PL IV) illustrates some of the cracks of 

plastered walls observed in St. James Hotel, San 

Jose. 

Secondary Cracks of the Ground. — Along the 

fault line the ground was, as in 

other cases, very often bulged 

up, forming a narrow zone of 

1 or 2 feet elevation and some 

5 or 10 feet width, as if raised 

up by a gigantic mole creeping 

underground. This sort of ridge, whose formation 

was due to the shearing action, combined with a 

compression along the line of dislocation, showed 
usually a series of secondary oblique 
cracks, as is diagrammatically indicated 
in Fig. 7. These ground cracks were 
perfectly similar to the shear cracks 
of walls considered above. 

Figs. 8, 9 and 10 show parts of the 
fault lines found near the town of Man- 
chester, not far from Pt. Arena; the 
dotted lines in each figure indicating 
the directions of the secondary shear 
cracks. Fig. 8 is the plan of the re- 
markable disturbances shown in Fig. 13. In Figs. 

9 and 10, the angle between the main fault line and 




Fig. ? 



[295] 



tf h e C ali f o r ni a Earthquake of i g o 6 

the shear cracks varied between 44° and 47°. In 
Fig. 8, however, there was evidently a very strong 
compression, and the shear angle was smaller, 
namely, 42°. 

I have measured the shear angle in eleven other 
cases, where it varied between 35° and 47° ; the 
total average value being 40°. 

If the shear be accompanied by a horizontal com- 
pression at right angles to the fault line, the angle 
between the latter and the shear cracks will be 
smaller than 45°, as suggested by Professor A. 
Inokuty, of the Engineering College, Tokyo Im- 
perial University. The coexistence of a tension 
normal to the fault plane will, on the other hand, 
make the same angle greater than 45°. 

io. Comparison with the Formosa Earthquake of 
March 17, igo6. The local but very severe earth- 
quake in the Kagi Prefecture, Formosa, on March 
17, 1906, produced also remarkable surface disloca- 
tions, in which the vertical depression and the 
horizontal shear each amounted to about 8 feet. 
The angle between the direction of the main fault 
and that of the shear cracks was on the average 43°. 

ii. Landslips, etc. In the meisoseismal area, 
there were great many cases of mountain slides. 
The most remarkable among these was that which 
occurred near Cape Fortuna (False Cape), where 
an enormous quantity of debris was detached from 

[296] 



N32'W 




N30V 



S32TS 



Fig. 8 — The Shaded Parts Indicate Cracks 
of the Ground. 








m 



D 



a mountain side and was pushed into the ocean, 
creating a new promontory of about % mile length. 

At Moss Landing, near Salinas, there were great 
horizontal disturbances of the sandy ground; the 
office of the station agent being displaced about 15 
feet relative to the adjoining fence. 

12. Direction of Motion in San Francisco. Fig. 19 
(PL VII) shows the directions towards which 520 
monuments at the different 
cemeteries in San Francisco 
and the vicinity were over- 
turned by the earthquake 
shock. It will be observed that 
the greatest number of the 
monuments were overturned 
towards the east or east 
slightly north. The mean di- 
rection of overturning is 
N76°E, which may be regarded 
as the direction toward which 
zontal displacement took place. 

ij. Relation to the Great Fault of the Directions 
of Motion at the Neighboring Places. The approximate 
directions of the principal or strongest motion at 
the different places on or near the fault, each deter- 
mined from numerous overturned bodies, were as 
follows : — 



siow 




the 



greatest 



Fig. 10. 



hori- 



299 



T* h e California Earthquake of i g o 6 






A.\ 



B 



' San Francisco N76°E. 

San Jose N81°E. 

Chittenden N38°E. 

Watsonville NE. 

Santa Rosa N. 

Tomales N. 

L Pt. Reyes Station (East side of Fault) . S. 

r Pt. Arena NNW. 

Inverness NW. 

Pt. Reyes Station(West side of Fault). .WWN. 

Wrights . N 

The mean general direction of the fault is N 37° 
W — S37°E, this being exactly identical with the 
direction of the great depression zone before men- 
tioned. The places in Group A are situated on the 
eastern side of the fault line, while those in Group 
B are situated on the western side. It will thus be 
observed that at the A. Group places the direction 
of motion was mostly towards north-northeast, 
or northeast by east; while at the B Group places, 
the direction was toward northwest, north, or 
northwest by west. Thus, on the whole, the mo- 
tion on each side of the fault line had a tendency 
to diverge, or to be directed away, from the latter. 
This can be explained on the supposition of a sub- 
terranean collapse, or settling down, which would 
produce an initial inward motion, to be followed 
by the second and larger outward displacement. 

[300] 



PL. III. 




Fig. ii — The Shearing Effects on a Pier at Inverness, on the West Coast 
of the Tomales Bay. The End Part of the Pier Was Displaced 
About 20 Feet Towards NNW. 



„..-■ 




m^ 



Fig. 12 — One of the Fault Cracks Produced Among the Hills Above Fort 
Ross. The New Disturbances Appeared Along a Depression Marked 
by a Series of Small Ponds (Shown at the Right-Hand Side of the 
Picture), Which Are Traces Left by a Former Earthquake. 



F . O m o r i , S c . D . 

Further, the directions of motion at the different 
places were mostly northward, and not southward. 
This would mean that the whole meisoseismal zone 
was first pushed towards SSE, the second or coun- 
ter motion, which was greater, being consequently 
directed toward NNW. I presume, therefore, that 
the action which caused the great earthquake of 
April 18th was a sudden movement towards south- 
east by south of the earth's crust at the west coast 
of California, accompanied by some downward 
thrust. In this connection it is extremely interest- 
ing to note that Mount Tamalpais, on the north 
shore of the Golden Gate, has been ascertained from 
trigonometrical measurements, to have moved, be- 
tween 1851 and 1882, 5.6 feet towards N12°W, in- 
dicating that the earth's crust at this part of 
America was being strained toward the same direc- 
tion. The ground on the eastern side of the fault 
line was generally displaced toward SSE relative 
to the ground on the other side; the amount of the 
horizontal slip was maximum at places between Pt. 
Arena and Pt. Reyes Station and varied from 16 ft. 
to 20 ft. ; the amount of displacement decreasing to 
about 8 ft. at Woodside, near Stanford University, 
and to about 4 ft. in the vicinity of Wrights. From 
the uniformity of northward direction of motion it 
is probable that both sides of the fault line were dis- 
placed toward NNW, but the west side was moved 

[ 303 ] 



< f h e California Earthquake of i g o 6 

more than the east side, the amount of the horizon- 
tal slip, or shear, above mentioned, being merely 
relative or differential. In the majority of cases the 
eastern side was depressed, the maximum amount 
being 2 feet. 

14. Depth of the Disturbance. From the compara- 
tively very small number of after-shocks, I am in- 
clined to suppose that the main source of the earth- 
quake was situated some considerable depth below 
the surface. In fact, the earthquake seems to have 
been caused by a disturbance which took place 
along the old weak line, but extended deeper into 
the earth's crust. The great depth of the main 
source of disturbance also explains why the inten- 
sity of motion was comparatively not very violent, 
and also why some places, such as Santa Rosa, San 
Jose and Ferndale, not directly on the fault zone, 
were also badly shaken. 

75. Earthquake Damage. This earthquake en- 
abled us, for the first time, to study the effects of the 
shocks on steel-brick and reinforced concrete build- 
ings; there being also numerous other damaged 
structures, such as ordinary brick, stone and 
wooden houses, bridges, water-pipes, etc. In San 
Francisco the earthquake was followed by fires, 
which broke out from several places, continued for 
three days, and entirely destroyed the principal 
business quarters of the city. The total area of the 

[304] 



PL. IV. 




Fig. 13 — Remarkable Compression and Shear Effects Along One of the 
Fault Cracks, Produced on Elevated Grounds Near Pt. Arena. A 
Foot-Scale Placed in the Foreground Shows the Size of the Over- 
lapping Earth Pieces, Whose Plan Is Given in Fig. 8. 




Fig. 14 — Some of the Cracks of Plastered 
San Jose. 



Walls, in St. James Hotel, 



t 



F . m o r i , S c . D . 

burned districts was 4.1 square miles, which is 
equivalent to 6 times the area of the great London 
fire of 1666. The amount of casualties was, how- 
ever, comparatively small, the ascertained number of 
persons killed being 390. The total number of the 
killed in the whole earthquake area was probably 
not more than 1000, the loss of life in Santa Rosa, 
Stanford University, and other strongly shaken 
places being slight. In San Francisco serious dam- 
age was confined to the filled-up grounds, where the 
motion was not so strong as in the cities of Nagoya 
(max. acceleration=2600 mm. per sec, per sec), 
Fukui (max. acceleration=2500 mm. per sec. per 
sec), etc., on the occasion of the great Mino-Owari 
earthquake of 1891. The double amplitude of mo- 
tion in San Francisco was probably some 4 inches, 
and the complete period of vibration about 1 second. 

Fig. 15 shows the damaged condition of the 
newly erected Library of the Stanford University. 
The central steel dome, which is virtually an elastic 
inverted pendulum, evidently much vibrated, 
thereby causing destruction to loosely connected 
brick and stone parts of the building. The mortar 
used for cementing the masonry walls was of an 
exceptionally bad quality. 

The damage to the City Hall of San Francisco 
was also principally due to the same two circum- 



[307 



*¥ h e California Earthquake of i g o 6 

stances, namely, the vibration of its high steel 
tower, and the bad quality of mortar. 

Fig. 16 (PL V) shows the ruined condition of a 
steel-framed brick house in San Francisco, which 
was dynamited and then burned. The effect of 
the intense heat is remarkable, the steel frames be- 
ing distorted in every possible form, as if they had 
been formed of a soft malleable metal. 

Fig. 17 (PL VI) gives an outside view of the back 
part of the Observatory on the top of Strawberry 
Hill, in the Golden Gate Park, San Francisco. This 
building is of reinforced concrete and furnishes a 
good demonstration of the strength of such 
structures. The Observatory was indeed seriously 
damaged and its front portion fell down to the 
ground, but this was on account of the weakness of 
the foundation ground, which was mostly a filled-up 
one and was considerably cracked and depressed. 
Fig. 18 shows, in a larger scale, one of the cracks of 
the basement wall, similar to that shown in Fig. 17. 
The steel cable, one inch in diameter, which was 
embedded in the concrete, was broken. The use of 
steel cables in concrete walls thus seems to be ob- 
jectionable, as they are more liable to rusting than 
solid steel bars. None of the latter used in the con- 
crete walls and floor of the Observatory, whose sec- 
tion was half inch square, was found broken; the 
adhesion of concrete and steel being also very good. 

[308] 



PL. V. 




Fig. 15 — The Damaged Condition of the Newly Erected Library of the Stanford 
University. The Central Steel Dome Behaved as an Elastic Inverted 

Pendulum. 




Fig. 16 — The Ruined Condition of a Steel-Framed Brick House in San Fran- 
cisco, Which Was Dynamited and Then Burnt, Showing the Remarkable 
Effects of the Intense Heat. 



i 



F . O m o r i , S c . D . 

16. Recent Seismic Activity. Recently there have 
been a number of great earthquakes in different 
parts of the world, especially along the following 
two zones : — 

(A). The Pacific coast of North and South 
America. 

(B). Himalayas and North Mediterranean zone. 
Next two sections give a short account of the earth- 
quakes belonging to these two zones. 

jy. Earthquakes along the West Coast of North and 
South America. Within the 7 years preceding the 
California earthquake of April 18, 1906, there 
were, along the Pacific coast of the American con- 
tinents, seven great earthquakes, on the dates as 
follows : — 

f (i) Sept. 4 and 11, 1899; and Oct. 9, 1900. 
I (ii) Jan. 20, 1900; and April 19 and Sept 23, 
1902. 
(iii) Jan. 31, 1906. 

Of the above seven earthquakes, the three of 
group (i) took place off the southwest coast of 
Alaska, two of them being accompanied by great 
tidal waves. The three earthquakes of the group 
(ii) strongly shook Mexico and Guatemala (Cen- 
tral America) ; while the earthquake of group (iii), 
which was accompanied by tidal disturbances, 
caused considerable damage in Panama, and the 
west coast of Columbia and Ecuador. The 

[3ii] 



T* h e California Earthquake of i g o 6 

approximate positions of these three groups of 
earthquakes are marked in Fig. 20 by dotted lines, 
/, 2, and j. 

As the west coast of the American continents is 
one of the great seismic zones on the earth, it is to 
be supposed that the seven destructive earthquakes 
above enumerated were not separate or local phe- 
nomena, but were the results of great stresses go- 
ing on along the Pacific coast zone, extending from 
Alaska to South America, manifested at its north 
and middle parts. Hence an event most naturally 
to be expected would have been the extension of the 
seismic disturbance to the west coast of the United 
States, which so far had been free from the visita- 
tion of disastrous earthquakes. This apprehended 
event finally took place on April 18, 1907, the 
approximate position of the origin being indi- 
cated in Fig. 20 by a thick line marked 4. The 
great California earthquake may, therefore, be 
regarded as having completed the continuity 
of the seismic activity along these districts, 
which latter thus become, for a certain number of 
years, say 20 or 30 years, seismically a very safe 
place ; large earthquakes, which remove a great un- 
stability in the earth's crust, never happening suc- 
cessively at once and the same place. 

During my recent stay in San Francisco I ex- 
plained on several occasions reasonings like the 

[312] 



PL. VI. 




Fig. 17 — The Observatory on the Top of the Strawberry Hill, in the Golden 
Gate Park, San Francisco, Built of Reinforced Concrete. An Outside View 
of the Back Part. 











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Fig. 18 — On* 0/ f/ie Cracks of the Basement Wall. The Steel Cable, One Inch 
in Diameter. Which Was Embedded in the Concrete, Was Broken. 



I 






IP . 







m 



D 






above to newspaper reporters and others, also 
pointing out that even in the case of a future 
destructive earthquake, the intensity of motion 
would not be extremely violent, so that a slight 
amount of precaution taken in building houses 
would ensure an almost perfect immunity from 

earthquake shocks. As 
to the probable position 

•^^^r^> of the next & reat shock 

on the Pacific side of 
America, I expressed my 
view that it would be to 
the south of the equator 
(that is to say, Chile and 
Peru),* as it was very 
likely that the seismic 
activity would extend to 
either end along the 
great zone in question, 
and as the coasts of the 
countries above named are often visited by strong 
earth convulsions. I departed on August 4th 
from San Francisco for home, and arrived on 
the 22d of the same month at Yokohama, first there 
learning of the disastrous shock of Valparaiso, 
which confirmed my anticipation. The approxi- 
mate position of the origin of this last earthquake, 

* This is what I published in the San Francisco Bulletin of June 
13, 1906. 

[315] 







tf h e California Earthquake of i g o 6 

which took place on August 17, 1906, is indicated in 
Fig. 20 by a thick line marked 5. 

The great stresses going on along the whole Pa- 
cific coast of America, which thus resulted in the 
occurrence of a series of great earthquakes, seem 
to be connected with the growth of the Rocky and 
Andes mountain ranges; the Valparaiso earthquake 
bringing probably the great seismic activity along 
the zone under consideration for the time to an end. 

18. Activity along the Himalayas and North Med- 
iterranean Zone. With regard to the seismic ac- 
tivity in Asia and Europe, it is to be noted that the 
unusually severe eruptions of Vesuvius, which 
began on about April 7, 1906, lasted about one 
week, and ended on the 13th of the same month. 
On the following day, namely April 14th, 
there took place the destructive earthquake of 
Kagi District (Formosa), in which 1249 persons 
were killed. Four days later there took place the 
great California earthquake. Whether or not 
there existed a connection between the Vesuvian 
eruption and these earthquakes, it is a matter of 
fact that there was a great seismic activity along 
the whole length of the zone extending from the 
north coast of the Mediterranean to the Himalayas, 
and possibly to Formosa. The different earth- 
quakes belonging to the zone in question, which 
happened recently, are as follows : 

[316] 



F . m o r i , S c . D . 

(i) Assam and Bengal (India), June 12, 
1897. 

(ii) Aidin (Smyrna), Sept. 20, 1899. 

(iii) Schemacha (Caucasus), Feb. 13, 1902. 

(iv) Kashugar (Turkestan), Aug. 22, 1902. 

(v) Saloniki (Macedonia), April 4, 1904. 

(vi) Kagi (Formosa), April 24, 1904. 

(vii) Kagi (Formosa), Nov. 6, 1904. 

(viii) Kangra Valley (the Punjab, India), 
April 4, 1905. 

(ix) Calabria (Italy), Sept. 8, 1905. 

(x) Kagi (Formosa), March 17, 1906. 

(xi) Kagi (Formosa), April 14, 1906. 
Thus great earthquakes took place at the dif- 
ferent parts of the zone stretching through Italy, 
Macedonia, Asia Minor, Caucasus, Turkestan, the 
outer side of the Himalayas, and Formosa; this 
proving that the underground stresses were grow- 
ing along the whole zone. As the seismic disturb- 
ances above enumerated occurred in the same 
epoch as those belonging to the American zone, it 
is extremely likely that underground stresses 
reached a maximum all over the earth, resulting in 
a marked display of seismic disturbances along 
certain zones of weakness. 

ig. Conclusion. Future studies in various phe- 
nomena connected with the movements of the 
earth's crust might perhaps tend to advance our 

[3i7] 



*? k e California Earthquake of i g o 6 

knowledge respecting the problem of the prediction 
of great earthquakes, which are often preceded by 
what may be called "fore-shocks." In the mean- 
while, and always, it will be necessary to build 
houses and other structures strong enough to resist 
earthquake shocks, a problem which presents no 
great difficulties. 

tfokyo, Nov. t, igo6. 



^aap^ 






318 



The Great Earthquake Rift of 
California 

By 

Harold W. Fairbanks, Ph.D. 

Reprinted from the Bulletin of the California Physical Geography Club 
October, IQO? 



\ 



1 



The Great Earthquake Rift of 
California 



WHICHEVER way we turn we are con- 
stantly impressed by the fact that the sur- 
face of the earth, with all its varied fea- 
tures, is undergoing continual change. The forces 
without, tearing down the mountains and carrying 
their materials to the lowlands, as a usual thing 
act slowly and quietly; but the forces within are 
frequently violent as they build up lofty volcanoes 
or break the crust and raise it in precipitous blocks. 
Although we dread earthquakes with all their 
resultant destruction, yet it is well to recognize the 
fact that if it were not for them we would find here 
in California little of that wonderful scenery of 
which we are so proud. Our earthquakes are due 
to movements similar to those which, through hun- 
dreds of thousands of years, have been raising the 
lofty mountains of the Cordilleran region. The 
Sierra Nevada range, with its abrupt eastern scarp 
nearly two miles high, faces an important line of 
fracture along which movements have continued to 
take place up to the present time. The Owens 
Valley earthquake of 1872 was the most recent on 

[321 ] 



°r h e California Earthquake of i g o 6 

this line and gave rise to a vertical displacement of 
10 to 40 feet. 

The presence of another line of weakness in the 
earth's crust was brought forcibly to our attention 
in April, 1906, and, although it has not yet resulted 
in the formation of a continuous line of lofty moun- 
tains, it may eventually do so. The great earth- 
quake rift of California is the most remarkable 
thing of its kind known in the world. This rift or 
fracture in the crust of the earth extends in a north- 
west and southeast direction for 700 miles across 
California. The rift lies for the most part in the 
Coast Ranges, but passes into the ocean upon the 
north and the Colorado desert upon the south. 

The rift must not be conceived of as an open 
fissure, for the walls are tight. The earth has 
broken under stress, and the walls upon opposite 
sides of the break slipped upon each other until the 
strain was in large part relieved. The earth move- 
ments have been of a complex nature, so that, while 
in places no vertical displacement appears to have 
taken place, in others it has produced escarpments 
300 to 400 feet high. The walls of the fissure not 
being absolutely even and straight, they would 
grind upon each other where two convex surfaces 
came together, producing a ridge upon the surface 
of the earth. Where two concave surfaces came 
opposite each other, the earth would cave in, giving 

[322] 



Harold W . Fairbanks, Ph.D. 

rise to hollows upon the surface. Thus we have 
produced along the rift peculiar features not due to 
the ordinary forces of erosion, features constituting 
what we might call "earthquake topography." 




Lake in a Sunken Area on the Rift in Cholame Valley. 

The clay formed by the grinding of the walls 
cuts off underground water-courses, forcing the 
water to the surface and forming springs, which 
along the more arid portions of the rift are among 
the most characteristic features. In the hollows 
due to the sunken earth the water collects and 

[323] 






T* h e California Earthquake of i g o 6 

gives rise to ponds and lakes. The presence of 
these peculiar features enables us to trace the rift 
throughout its whole course. 

As a matter of fact, certain portions of the great 
rift have been known to the country people living 
along it for many years. Especially is this true of 
the southern portion, which opened in 1857, and 
that lying in San Benito County, which has opened 
several times since that date. Previous to the 
earthquake of April, 1906, the writer had traced 
the rift for fully 400 miles. When the last earth- 
quake came, the northern portion of the rift then 
known opened again, and, in addition, directed our 
attention to nearly three hundred miles more of its 
course which had not previously been explored. 

A remarkable thing in connection with the recent 
earthquake was the horizontal movement of the 
walls of the fissure. In most fault fissures the 
movement has been vertical or oblique, as is shown 
by the striations upon the walls, but in the present 
instance there appears to have been no general ver- 
tical component. Wherever scarps appear they are 
local and due either to the settling of the earth upon 
a hillside or to the sagging of the earth where the 
movement brought two concave surfaces together. 

The eastern wall of the great rift moved south 
and the western wall moved north a distance dimin- 
ishing from 16 feet near Point Arena to 4 feet south 

[324] 



Harold W . Fairbanks, Ph.D. 

of the Pajaro Canon, San Benito County, and to 
nothing near the town of San Juan. It is clear that 
less than half of the known rift opened during the 
recent disturbance. It is probable from what can 




Effect of Recent Earthquake in the Ridge Above Mussel Rock. 



be learned that the whole southern portion of the 
rift opened in the earthquake of 1857, while at least 
two local openings have occurred in the middle por- 
tion in San Benito County between the dates of the 
two great earthquakes referred to. 

We have no idea of the date of the original open- 

[325] 



tf h e California Earthquake of i g o 6 

ing of the rift. The so-called "earthquake topog- 
raphy" by which we trace the rift had its inception 
hundreds of years ago, for huge oaks are grow- 
ing upon it in places. The origin of the fault 
fissure was undoubtedly far back in the geological 
history of the region. Along many portions of the 
rift there are faults showing a vertical displacement 
of more than 1000 feet, the effects of which do not 
appear at all in the present topography. 

The crushed and broken rocks along the rift are 
more easily eroded than solid rocks, and this has 
given rise to canons and valleys, which for many 
miles mark certain portions. These features have 
determined the location of roads and trails. The 
springs also have determined the position of houses 
and ranch buildings. Thus for years the rift fea- 
tures have had their influence upon people without 
the latter recognizing their meaning and import- 
ance. The effect of the rift upon the water supply 
is most noticeable through the Mohave Desert and 
San Bernardino Valley. The rift extends for many 
miles along the northern base of the Sierra Madre 
in the edge of the Mohave Desert. The under- 
ground waters seeping down the valleys are forced 
to the surface by the impervious clays, and thus 
give rise to valuable springs, cienegas and ponds. 
These become of extreme value in a region where 
the lack of water is the only bar to settlement. 

[326] 



Harold W . 



i r b a n k s , Ph.D. 



The northernmost point where the rift has been 
observed is upon the projecting headland near Shel- 
ter Cove, southern Humboldt County. Thence 
southward for some fifty miles it lies in the ocean 




Road Displaced 12 Feet on Line of Rift at Head of Tomales Bay. 

a short distance off-shore. The rift comes inland 
again at the mouth of Alder Creek near Point 
Arena. The valleys of the Garcia and Wallala 
mark its southward course, and two miles southerly 
from Fort Ross it enters the ocean again. Passing 
across Bodega Head, the course of the rift carries 

[ 327 ] 



', 



T ' h e California 'Earthquake of i g o 6 

it the whole length of Tomales Bay, then through 
the valley-like depression leading over to Bolinas 
Bay. 

The rift lies about a mile off-shore opposite the 
Golden Gate, but at Mussel Rock, six miles south- 
ward, it encounters the land, and from this point, 
as we follow its course, it carries us farther and 
farther inland. 

From Mussel Rock to San Andreas Lake the rift 
is marked by a series of ponds and small lakes. 
Back of Stanford University the rift traverses the 
Portola Valley, and there it is known as the "Por- 
tola fault." The course pursued finally takes it 
over the Santa Cruz Range and down to the Pajaro 
Canon at the point where the latter is spanned 
by the Southern Pacific Railroad bridge. The 
horizontal movement was here about 4 feet, and it 
is interesting to note that the rift opened between 
the western abutment and the adjoining pier, in- 
creasing the distance between the two so much that 
the iron girders nearly dropped into the river. 

The town of San Juan, San Benito County, is 
situated most peculiarly with reference to the rift 
line, and, although many farm buildings owe their 
position to conditions of the rift, this is the only 
town whose location has been determined by it. 
The town lies upon a slight eminence in the broad 
valley of the San Benito River. A detailed exami- 

[328] 



Harold W . Fair 



a n 



Ph.D. 



nation shows that this eminence slopes gently to 
the southwest, while upon the northeast there is a 
steep and regular bluff fifty feet high. The exist- 
ence of springs at the base of the bluff, and the fact 




Alkali Sink on Line of the Rift North of Baker sfield. 



that it lies directly in the line of the rift, as well as 
the general resemblance of the eminence to known 
fault blocks, make it reasonable to assume that 
such is its origin. 

From San Juan we trace the rift on its regular 
southerly course along the northern slope of the 

[329] 






': 



*f h e California Earthquake of i g o 6 

Gavilan Range. Near the head of San Juan Canon 
movements along the rift have led the stream which 
occupied the canon to break over a low spot in the 
water-shed and, as a consequence, it abandoned the 
lower part of the canon and now flows directly 
down the mountain toward Hollister. 

A few miles farther on we reach Cienega Valley, 
where the uplift of the northern wall of the rift has 
made a dam across a valley. Back of this dam, 
gravel has collected, forming an underground 
reservoir, from which the town of Hollister gets 
its supply. 

Earth movements have made the rift in this sec- 
tion the most suitable place for a road, therefore 
we follow it most of the way to the San Benito 
River and then up the valley of this stream for 
many miles. Shortly after reaching the river we 
come to a remarkable depression, nearly a mile 
long, due to subsidence during some one of the vio- 
lent disturbances of long ago. By means of ridges, 
hollows, and ponds, the rift is traced in a direct line 
to Bitterwater, Monterey County. 

South of San Benito Postofrice appears a fault 
block similar to, although much larger than, the 
one at San Juan. This fault block has an abrupt 
eastern slope, two hundred feet high, along the 
side of which the road runs. It has a long, 
gentle slope toward the west. This fault block is a 

[330] 



Harold W . Fairbanks, Ph.D. 

good representation in miniature of the great 
Sierra Nevada fault block. 

Next on the line which we are following lies Dry 
Lake Valley, comprising an area of considerable 
extent, which has been so disturbed by earth move- 
ments that it has no external drainage. Looking 
southeasterly from this valley we see a precipitous 
mountain profile in the distance and directly on the 
line of the rift. Upon examination this appears to 
be the product of some earthquake movement. 
Across one small valley the road follows the top of 
a ridge which has a striking resemblance to an old 
railroad embankment. 

Bitterwater Valley is partly occupied by a lake 
during the wet season as a result of earth disturb- 
ances. Where the rift crosses Lewis Creek there 
is an enormous landslide which nearly blocks the 
valley. Along the mountain ridge north of Peach 
Tree Valley there are many landslides, and in Stone 
Canon rapidly eroding slopes testify to compara- 
tively recent movements. 

The rift traverses Cholame Valley in eastern 
Monterey County. Near Parkfield the surface over 
a considerable area bears evidence of having been 
greatly broken up. A branch rift with two parts, 
one marked by the front of a line of hills and the 
other by depressions and lakes, is traceable for 
several miles in a more easterly course. West of 

[33i] 



T* h e California Earthquake of i g o 6 

Parkfield a giant oak, undoubtedly many hundreds 
of years old, stands upon a low ridge which 
marks the main rift. At this place there is a spring 
and a pretty home, the one due to, the other made 
possible by, the existence of the earth fracture. 

From the lower end of Cholame Valley the rift 
passes over rolling hills until it reaches the Carrisa 
Plain, down whose length it runs for fifty miles. 
The southern twenty miles of its course across 
this desert plain is marked by a line of hills from 
two to three hundred feet high, which undoubtedly 
are the product of some movement in the remote 
past. 

As we trace the line farther south, the topog- 
raphy indicates profound movements. A consider- 
able area west of the Sunset oil district has had its 
drainage so disturbed that with the light rainfall in 
this region the streams have never broken across 
the ridges formed by the earth movements. The 
depressions are occupied by water during excep- 
tionally wet years, but for the most of the time they 
are white alkali sinks. 

Throughout nearly the whole course of the rift 
between the Cholame Valley and the valley of San 
Bernardino there may be seen the nearly obliterated 
effect of the Tejon earthquake of 1857. This is a low 
scarp or ridge, at the foot of a higher ridge of an 
earlier time. At one point in the Carrisa Plain four 

[332] 



Harold W . Fairbanks, Ph.D. 

or five earthquake ridges appear within a width 
of a quarter of a mile. 

Passing up a canon fully three thousand feet deep, 
which is without doubt due to faulting in recent 
geological time, the rift crosses the San Emedio 
Mountains through the head of the canon of the 
same name. Along this stretch it forms springs. 

Passing over the divide at the head of the east 
fork of the San Emedio Canon, we reach Cuddy 
Valley, where the sinking of a block of the earth, 
now a fertile well-watered valley, has led to the 
creation of an escarpment some miles long and from 
one hundred to three hundred feet high. Upon this 
escarpment old pine trees are standing. 

Going to Tejon Pass we continue down a long 
canon, whose northern walls have been greatly 
shattered by earthquakes. In this canon we note 
the formation of great debris fans at the mouths of 
the gulches, the material having been derived from 
the broken rocks. 

The rift makes a great turn to the east, across 
the San Emedio Mountains, but at Tejon Pass it 
turns again to a southeasterly direction, which it 
follows very regularly for two hundred miles. 

For several miles southeast from Gorman Sta- 
tion, which lies just east of Tejon Pass, the old 
Los Angeles-Bakersfield stage road follows the 
valley of the rift. 

[ 333 ] 



tf h e Calif or n i a Earthquake of i g o 6 

In the earthquake of 1857 this road is reported to 
have been seriously broken up, and the surface at 
the present time seems to verify the statement. A 
few miles southeast of Gorman Station the rift 
passes out to Antelope Valley (the western arm of 
the Mohave Desert), skirting the lofty mountains 
which rise on the south. 

By means of springs, cienegas, and long, narrow 
valleys, we trace the rift to a point one mile south 
of Palmdale, a station on the Southern Pacific Rail- 
road. The rift passes through Lake Elizabeth, the 
largest body of water in this part of California. 
The lake itself is due to the interference of earth 
movements with the drainage of a broad valley. 

Near Palmdale are interesting ridges and sinks. 
One of the latter is so large that it has been used as 
a reservoir to store water for irrigation. Looking 
from the ridge where the railroad crosses the rift, 
we can follow its course for many miles by a break 
in the slope of the desert wash. 

Strikingly interesting features appear as we 
climb the northern flanks of the San Gabriel Range 
and pass out of the desert into the pine forests. At 
one spot a ridge has been split away from the 
mountain, making two streams where there was 
formerly only one. Upon this ridge there are large 
pine trees. 

At an elevation of seven thousand feet we cross 

[334] 



Harold W . Fairbanks, Ph.D. 

over the San Gabriel Range and descend a long, 
straight canon, called Lone Pine, to the lower end 
of Cajon Pass. From here the rift marks the line 
between the lofty front of the San Bernardino 
Range and the gravel mesa leading down to the 
valley. Movements of the country upon either side 
of the rift have broken the mesa, producing ridges 
and scarps, some of which are over fifty feet high. 
Here, as throughout the course of the rift along the 
southern border of the Mohave Desert, the grinding 
movements have produced an impervious clay layer, 
which stops the waters coming down from the 
mountains and brings them to the surface, thus 
forming springs, cienegas, meadows, and lakes. The 
rift line is in fact one of the most important eco- 
nomic features of the desert region which it tra- 
verses, for nearly half its known length, producing 
surface water in a land where water is the most 
important consideration. 

As we stand in the valley and look at the lofty 
San Bernardino Range, we can readily imagine its 
slow growth by repeated earthquake movements 
through the long ages of the past and how the 
region looked when the ancient and nearly worn- 
down mountains of the present Mohave Desert ex- 
tended unbroken across to the sea and far to the 
south. 

East of the point where the Santa Ana River 

[335] 






I 



the California Earthquake of i g o 6 

issues from the mountains a stream of considerable 
size has been compelled to form a new channel as 
a result of the uplift of the mesa gravels. 

Beyond the Santa Ana River, in the direction of 
Potato Canon, the features of the rift become more 
indistinct and in places are nearly obliterated. 
Crushing and breaking of the rocks on these steep 
mountain slopes has led to such rapid erosion that 
surface changes are comparatively rapid. 

Southeast of Potato Canon the rift line begins 
to turn more easterly and, instead of descending 
to and crossing the San Gorgonio Pass and then 
skirting the east base of San Jacinto Mountains, 
as it was at first thought to do, it was found to keep 
along the side of the mountains north of the pass 
and finally to disappear in the desert wash east of 
the Whitewater River. Where last seen, the course 
was due east, a direction which would carry it 
north of Palm Spring Station in the Conchilla 
Desert. While it is doubtful if the distinctive 
"earthquake topography" can be traced any far- 
ther, yet it is probable that a fault continues on still 
farther along the mountains lying north of the 
Salton Basin. 

Although we think the earthquake of April, 1906, 
was severe, it was undoubtedly light when com- 
pared with many that have occurred along the 
same line. It will not be many years before the 

[336] 



Harold W . Fairbanks, Ph.D. 

surface effects of the last earthquake will have gen- 
erally disappeared. The effects of the Tejon 
earthquake are still visible although it took place 
fifty years ago. Imagination alone can picture the 
destructive effects of an earthquake which could 
form scarps 100 to 300 feet high. 



[337] 



The Temblor 

A Personal Narration 
By 

Mary Austin 






' 



The Temblor 



THERE are some fortunes harder to bear once 
they are done with than while they are doing, 
and there are three things that I shall never 
be able to abide in quietness again — the smell of 
burning, the creaking of house-beams in the night, 
and the roar of a great city going past me in the 
street. 

Ours was a quiet neighborhood in the best times; 
undisturbed except by the hawker's cry or the sel- 
dom whistling hum of the wire, and in the two days 
following April eighteenth, it became a little lane 
out of Destruction. The first thing I was aware of 
was being wakened sharply to see my bureau lun- 
ging solemnly at me across the width of the room. 
It got up first on one castor and then on another, 
like the table at a seance, and wagged its top por- 
tentously. It was an antique pattern, tall and 
marble-topped, and quite heavy enough to seem for 
the moment sufficient cause for all the uproar. 
Then I remember standing in the doorway to see 
the great barred leaves of the entrance on the sec- 
ond floor part quietly as under an unseen hand, and 
beyond them, in the morning grayness, the rose 

[34i] 



tf h e California Earthquake of i g o 6 



tree and the palms replacing one another, as in a 
moving picture, and suddenly an eruption of night- 
gowned figures crying out that it was only an earth- 
quake, but I had already made this discovery for 
myself as I recall trying to explain. Nobody having 




San Francisco on the Night of April 18. 

suffered much in our immediate vicinity, we were 
left free to perceive that the very instant after the 
quake was tempered by the half-humorous, wholly 
American appreciation of a thoroughly good job. 
Half an hour after the temblor people sitting on 
their doorsteps, in bathrobes and kimonos, were ad- 
mitting to each other with a half twist of laughter 
between tremblings that it was a really creditable 
shake. 

[342] 



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The appreciation of calamity widened slowly as 
water rays on a mantling pond. Mercifully the 
temblor came at an hour when families had not 
divided for the day, but live wires sagging across 
housetops were to outdo the damage of falling 




Looking Southeast from Telegraph Hill During Fire 



walls. Almost before the dust of ruined walls had 
ceased rising, smoke began to go up against the 
sun, which, by nine of the clock, showed bloodshot 
through it as the eye of Disaster. 

It is perfectly safe to believe anything any one 
tells you of personal adventure; the inventive fac- 
ulty does not exist which could outdo the actuality; 
little things prick themselves on the attention as 
the index of the greater horror. 

[343] 



T ' h e California Earthquake of i g o 6 

I remember distinctly that in the first considered 
interval after the temblor, I went about and took 
all the flowers out of the vases to save the water 
that was left ; and that I went longer without wash- 
ing my face than I ever expect to again. 

I recall the red flare of a potted geranium undis- 
turbed on a window ledge in a wall of which the 
brickwork dropped outward, while the roof had 
gone through the flooring; and the cross-section of 
a lodging house parted cleanly with all the little 
rooms unaltered, and the halls like burrows, as if 
it were the home of some superior sort of insect laid 
open to the microscope. 

South of Market, in the district known as the 
Mission, there were cheap man-traps folded in like 
pasteboard, and from these, before the rip of the 
flames blotted out the sound, arose the thin, long 
scream of mortal agony. 

Down on Market Street Wednesday morning, 
when the smoke from the burning blocks behind be- 
gan to pour through the windows we saw an Italian 
woman kneeling on the street corner praying 
quietly. Her cheap belongings were scattered be- 
side her on the ground and the crowd trampled 
them; a child lay on a heap of clothes and bedding 
beside her, covered and very quiet. The woman 
opened her eyes now and then, looked at the red- 
dening smoke and addressed herself to prayer as 

[344] 



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one sure of the stroke of fate. It was not until 
several days later that it occurred to me why the 
baby lay so quiet, and why the woman prayed in- 
stead of flying. 

Not far from there, a day-old bride waited while 




Looking South from Lafayette Square, 4 p. m. April 18 

her husband went back to the ruined hotel for some 
papers he had left, and the cornice fell on him; then 
a man who had known him, but not that he was 
married, came by and carried away the body and 
shipped it out of the city, so that for four days the 
bride knew not what had become of him. 

There was a young man who, seeing a broken 
and dismantled grocery, meant no more than to 

[345] 



tf h e California Earthquake of i g o 6 

save some food, for already the certainty of famine 
was upon the city — and was shot for looting. Then 
his women came and carried the body away, mother 
and betrothed, and laid it on the grass until space 
could be found for burial. They drew a handker- 
chief over its face, and sat quietly beside it without 
bitterness or weeping. It was all like this, broken 
bits of human tragedy, curiously unrelated, incon- 
sequential, disrupted by the temblor, impossible to 
this day to gather up and compose into a proper 
picture. 

The largeness of the event had the effect of re- 
ducing private sorrow to a mere pin prick and a 
point of time. Everybody tells you tales like this 
with more or less detail. It was reported that 
two blocks from us a man lay all day with 
a placard on his breast that he was shot for 
looting, and no one denied the aptness of the 
warning. The will of the people was toward 
authority, and everywhere the tread of soldiery 
brought a relieved sense of things orderly and 
secure. It was not as if the city had waited 
for martial law to be declared, but as if it precip- 
itated itself into that state by instinct as its best 
refuge. 

In the parks were the refugees huddled on the 
damp sod with insufficient bedding and less food 
and no water. They laughed. They had come out 

[346] 



»; 




ifl 


;'■","'' ■■'■■ 

r 


*A"* 


1 1* ! 






; .; *"«* 





Fo;i Afess Avenue, 10:30 p. m. April 10 




Jefferson Square 



Mary Austin 

of their homes with scant possessions, often the 
least serviceable. They had lost business and 
clientage and tools, and they did not know if their 
friends had fared worse. Hot, stifling smoke bil- 
lowed down upon them, cinders pattered like hail 
— and they laughed — not hysteria, but the laughter 
of unbroken courage. 

That exodus to the park did not begin in our 
neighborhood until the second day; all the first day 
was spent in seeing such things as I relate, while 
confidently expecting the wind to blow the fire an- 
other way. Safe to say one-half the loss of house- 
hold goods might have been averted, had not the 
residents been too sure of such exemption. It hap- 
pened not infrequently that when a man had seen 
his women safe he went out to relief work and re- 
turning found smoking ashes — and the family had 
left no address. We were told of those who had 
dead in their households who took them up and fled 
with them to the likeliest place in the hope of burial, 
but before it had been accomplished were pushed 
forward by the flames. Yet to have taken part in 
that agonized race for the open was worth all it 
cost in goods. 

Before the red night paled into murky dawn 
thousands of people were vomited out of the angry 
throat of the street far down toward Market. Even 
the smallest child carried something, or pushed it 

[349] 



tf h e California Earthquake of i g o 6 

before him on a rocking chair, or dragged it behind 
him in a trunk, and the thing he carried was the 
index of the refugee's strongest bent. All the 
women* saved their best hats and their babies, and, 
if there were no babies, some of them pushed pianos 
up the cement pavements. 

All the faces were smutched and pallid, all the 
figures sloped steadily forward toward the cleared 
places. Behind them the expelling fire bent out 
over the lines of flight, the writhing smoke stooped 
and waved, a fine rain of cinders pattered and 
rustled over all the folks, and charred bits of the 
burning fled in the heated air and dropped among 
the goods. There was a strange, hot, sickish smell 
in the street as if it had become the hollow slot of 
some fiery breathing snake. I came out and stood 
in the pale pinkish glow and saw a man I knew 
hurrying down toward the gutted district, the 
badge of a relief committee fluttering on his coat. 
"Bob," I said, "it looks like the day of judgment !" 
He cast back at me over his shoulder unveiled dis- 
gust at the inadequacy of my terms. "Aw!" he 
said, "it looks like hell!" 

It was a well-bred community that poured itself 
out into Jefferson Square, where I lay with my 
friend's goods, and we were packed too close for 
most of the minor decencies, but nobody forgot his 
manners. "Beg pardon!" said a man hovering over 

[35o] 






M 



A 



me with a 200-pound trunk. "Not at all!" I an- 
swered making myself thin for him to step over. 
With an "Excuse me, madam!" another, fleeing 
from the too-heated border of the park to its 
packed center, deftly up-ended a roll of bedding, 




"Nob Hill" After the Fire, Showing the Huntington, Crocker, and Flood Resi- 
dences. Fairmont Hotel in Background. 

turned it across the woman who lay next to me — 
and the woman smiled. 

Right here, if you had time for it, you gripped 
the large, essential spirit of the West, the ability 
to dramatize its own activity, and, while continuing 
in it, to stand off and be vastly entertained by it. 
In spite of individual heartsinkings, the San Fran- 

[35i] 



*¥ h e California Earthquake of i g o 6 

ciscans during the week never lost the spirited 
sense of being audience to their own performance. 
Large figures of adventure moved through the murk 
of those days — Denman going out with his gun 
and holding up express wagons with expensively- 
saved goods, which were dumped out on sidewalks 
that food might be carried to unfed hundreds; 
Father Ramm cutting away the timbers of St. 
Mary's tower, while the red glow crept across the 
charred cross out of reach of the hose; and the 
humble sacrifices — the woman who shared her full 
breast with the child of another whose fountain 
had failed from weariness and fright — would that 
I had her name to hold in remembrance! She had 
stopped in the middle of a long residence hill and 
rested on a forsaken stoop, nourishing her child 
quietly, when the other woman came by panting, 
fainting and afraid, not of her class, nor her race, 
but the hungry baby yearned toward the uncovered 
breast — and they both of them understood that 
speech well enough. 

Everybody tells you tales like, this, more, and 
better. All along the fire line of Van Ness Avenue, 
heroic episodes transpired like groups in a frieze 
against the writhing background of furnace-heated 
flame; and, for a pediment to the frieze, rows of 
houseless, possessionless people wrapped in a large, 
impersonal appreciation of the spectacle. 

[352] 




In the Apartment House District 




Tivoli Theatre 



I 



M 



From Gough Street, looking down, we saw the 
great tide of fire roaring in the hollow toward 
Russian Hill; burning so steadily for all it burned 
so fast that it had the effect of immense delibera- 
tion; roaring on toward miles of uninhabited dwell- 
ings so lately emptied of life that they appeared 
consciously to await their immolation; beyond the 
line of roofs, the hill, standing up darkly against 
the glow of other incalculable fires, the uplift of 
flames from viewless intricacies of destruction, 
sparks belching furiously intermittent like the 
spray of bursting seas. Low down in front ran 
besmirched Lilliputians training inadequate hose 
and creating tiny explosions of a block or so of 
expensive dwellings by which the rest of us were 
ultimately saved; and high against the tip of 
flames where it ran out in broken sparks, the figure 
of the priest chopping steadily at the tower with 
the constrained small movement of a mechanical 
toy. 

Observe that a moment since I said houseless 
people, not homeless; for it comes to this with the 
bulk of San Franciscans, that they discovered the 
place and the spirit to be home rather than the 
walls and the furnishings. No matter how the 
insurance totals foot up, what landmarks, what 
treasures of art are evanished, San Francisco, our 
San Francisco is all there yet. Fast as the tall 

[355] 



tf h e California Earthquake of i g o 6 

banners of smoke rose up and the flames reddened 
them, rose up with it something impalpable, like 
an exhalation. We saw it breaking up in the move- 
ments of the refugees, heard it in the tones of their 
voices, felt it as they wrestled in the teeth of 
destruction. The sharp sentences by which men 
called to each other to note the behavior of brick 
and stone dwellings contained a hint of a warning 
already accepted for the new building before the 
old had crumbled. When the heat of conflagration 
outran the flames and reaching over wide avenues 
caught high gables and crosses of church steeples, 
men watching them smoke and blister and crackle 
into flame, said shortly, "No more wooden towers 
for San Francisco!" and saved their breath to run 
with the hose. 

What distinguishes the personal experience of the 
destruction of the gray city from all like disasters 
of record, is the keen appreciation of the deathless- 
ness of the spirit of living. For the greater 
part of this disaster — the irreclaimable loss of 
goods and houses, the violent deaths — was due 
chiefly to man-contrivances, to the sinking of 
made ground, to huddled buildings cheapened 
by greed, to insensate clinging to the outer 
shells of life; the strong tug of nature was always 
toward the renewal of it. Births near their time came 
on hurriedly; children were delivered in the streets 

[356] 



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or the midst of burnings, and none the worse for 
the absence of conventional circumstance; mar- 
riages were made amazingly, as the disorder of the 
social world threw all men back severely upon its 
primal institutions. 




Fairmont Hotel After the Fire 

After a great lapse of time, when earthquake 
stories had become matter for humorous reminis- 
cence, burning blocks topics of daily news, and 
standing in the bread line a fixed habit — by the 
morning of the third day, to be exact — there arose 
a threat of peril greater than the thirst or famine, 
which all the world rose up swiftly to relieve. 

Thousands of families had camped in parks not 

[357] 



C Z° h e California Earthquake of i g o 6 

meant to be lived in, but to be looked at; lacking 
the most elementary means of sanitation. With 
the rising of the sun, a stench arose from these 
places and increased perceptibly; spreading with it 
like an exhalation, went the fear of pestilence. But 
this at least was a dread that every man could fight 
at his own camp, and the fight was the modern con- 
viction of the relativity of sanitation to health. By 
mid-morning the condition of Jefferson Square was 
such that I should not have trusted myself to it for 
three hours more, but in three hours it was made 
safe by no more organized effort than came of the 
intelligent recognition of the peril. They cleaned 
the camp first, and organized committees of sanita- 
tion afterward. 

There have been some unconsidered references 
of the earthquake disaster to the judgment of God; 
happily not much of it, but enough to make perti- 
nent some conclusions that shaped themselves 
swiftly as the city fought and ran. Not to quarrel 
with the intelligence that reads God behind seismic 
disturbance, one must still note that the actual 
damage done by God to the city was small beside 
the possibilities for damage that reside in man-con- 
trivances; for most man-made things do inherently 
carry the elements of their own destruction. 

How much of all that happened of distress and 
inestimable loss could have been averted if men 

[358] 



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would live along the line of the Original Intention, 
with wide, clean breathing spaces and room for 
green growing things to push up between? 

I have an indistinct impression that the calendar 
time spent in the city after the temblor was about 
ten days. I remember the night of rain, and seeing 
a grown man sitting on a curbstone the morning 
after, sobbing in the final break-down of bodily en- 
durance. I remember too the sigh of the wind 
through windows of desolate walls, and the screech 
and clack of ruined cornices in the red noisy night, 
and the cheerful banging of pianos in the camps; 
the burials in trenches and the little, bluish, grave- 
long heaps of burning among the ruins of China- 
town, and the laughter that shook us as in the 
midst of the ashy desert we poured in dogged 
stream to the ferry, at a placard that in a half- 
burned building where activity had begun again, 
swung about in the wind and displayed this legend: 



DON'T TALK EARTHQUAKE 



TALK BUSINESS 



All these things seem to have occurred within a 
short space of days, but when I came out at last at 

[359] 



the California Earthquake of i g o 6 

Berkeley — too blossomy, too full-leafed, too radi- 
ant — by this token I knew that a great hiatus had 
taken place. It had been long enough to forget 
that the smell of sun-steeped roses could be sweet. 



[360 



Index 

to the 

California Earthquake 
of 1906 






H 



Ind 



ex 

(Illustrations are marked with asterisk.) 



PAGE 

Absolute Movement of Crust ........ 113 

Agnews Asylum 185*, 186 

Alaska Earthquake 56 

Alder Creek, Mendocino County, Bridge at 10*, 13 

Alkali Sink, North of Bakersfield 329* 

American Society of Civil Engineers, Investigation by ... 82 

Antelope Valley . . . ._ 334 

Apartment House District, View of 353* 

Appraiser's Building 135 

Area of Destructive Motion ...... 284 

Artesian Wells 279 

Austin, Mary 339 

Azul Springs 69 

Belt of Main Disturbance 95 

Bitterwater Valley 331 

Black Mountain 268 

Bodega Head 106 

Bogoslof Islands 35, 45*, 36, 37, 39*, 41*, 43*, 44*, 45* 

Bolinas Bay 24 

Branner, John C 63 

Brick Bonding 211 

Brick Buildings 114, 131 

Brick Chimneys 131 

Brickwork 202 

California Earthquake, Cause of ... 283 

Center in Sea 9 

Destructive Extent of 81-212 

Effect at Sea : 10 

Investigation of 213 

Local Effects 257 

Note of Cause 281 

California Earthquakes, Catalogue of 52 

Character of 227 

Origin of 55 

Periodicity of 55 

California, Map Showing Fault Line 93* 

Relief Map of 3* 

Call Building 145 

Cantwell, on New Bogoslof 47 



363 



Index to the California Earthquake of igo6 



PAGE 

Cape Fortuna 296 

Cape Mendocino 35 

Carrisa Plain ... 332 

Carnegie Institution .- 220 

Castle Island 36* 

Cause of Earthquake 283 

Center of Disturbance 34 

Charleston Earthquake 227 

Chimneys 137, 138*, 203, 210 

Chittenden Ranch 29 

Cholame Valley 331 

Lake in 323* 

Cienega Valley 330 

City Hall, San Francisco 307 

Class A Buildings 141, 147, 210 

Class B Buildings 138, 140*, 210 

Classification of Ground 122 

Collapse by Compression 175 

Committees of Investigation 220 

Concrete Sewers 208 

Conduits 209 

Cornices 202 

Cowell Building, Fire Ruins of 140* 

Cracking 146, 149*, 151, 153*, 155* 

Cracks, Caused by Marshy Ground 235* 

In Basement Wall 313* 

In Ground 297* 

In Plastered Walls 305* 

In Road 243* 

Cross Faults 30 

Crust of Earth 99 

Crystal Springs, Conduit 97, 165, 166*, 167* 

Dam 162, 269* 

Reservoir 25, 72, 268, 269* 

Cuddy Valley 333 

Deformations 123 

Depth of Disturbance 304 

Derleth, Charles, Jr. . . 79 

Destructive Path of Fault Line 102 

Diagonal Framing 144, 210 

Diagonal Rupture 173*, 174* 

Diagrams, Illustrating Dislocation 228* 

Showing Geographic Changes 251* 

Differential Displacement 108, 112, 230 

Direction of Motion 291* 

Direction of Movement 274, 291* 

In San Francisco 299 

Its Relation to Great Fault 299 



[364 



Index to the California Earthquake of igo6 



PAGE 

Displacement 269*, 293 

Horizontal 5, 108 

Lateral 264 

Measurement of 230 

Vertical 5, 112 

Dry Lake Valley 331 

Duxbury Reef, Sea-Bottom Raised at 25 

Earthquakes, in Alaska 56 

Along West Coast 311 

At Valparaiso 56 

Damage by 158, 304 

Distinguished 1, 87 

Electrical Theory of 57 

Engineering Interest in 83 

Future Possibility of 255 

Japan, of 1891 284 

Loss of Life in 307 

Of North Mediterranean Zone 316 

Of 1868 61 

Of 1872 91 

Theories of 76 

Earthquake Commission 51, 81 

Earthquake Crack, in County Road 16* 

At Freeman's Ranch 18*, 17* 

Earthquakes and Crustal Movements 85 

Earthquake, Personal Narrative of 341 

Earthquake Rift, in Turf 233* 

At Alder Creek Bridge 10* 

At Morrill's Ranch 26*, 28* 

At Olema 22* 

At Point Arena 6 

At Shafter Ranch 75* 

House Located Over 70* 

In Road near Bolinas ... 234* 

In Road near Skyland 67* 

Near Azul Springs 69* 

Of 1906 1-62 

Possible Connection with Bogoslof 35 

Earthquake, Stresses 143 

Topography 323 

Theories 76 

Vibration 146 

Weather 60 

Effect of Topography and Structure 95 

Elasticity 133 

Electric Insulation 212 

Electrical Theory of Earthquakes, Hallock on 57 

Engineering Conclusions 200 



[365 



Index to the California Earthquake of igo6 



PAGE 

Epifocal Zone 289 

Center of 286 

Fairbanks, Harold W 319 

Fairmont Hotel, After the Fire 357 

Cracking in 153* 

Fault 100, 289 

Fault Block 330 

Fault Crack 301 

Fault Lines, in California 88 

Destructive Path of 102 

Map of 93, 159*, 217* 

South of Fort Ross 106 

Fault Topography 221* 

Faulted Road 264*, 234*, 235*, 231*, 243* 

Faulted Valleys 7 

Faulty Construction 120 

Fence, Crossing Fault at Oblique Angle 265* 

Crossing Fault at Right Angle 267* 

Near San Andreas 112* 

Showing Break and Offset 12*, 109*, 225*, 266* 

Ferry Building, Cracking on Piers of ... 155* 

Tower of 156, 157* 

Filled Ground ....... 97, 122, 124, 154, 239*, 238, 245, 307 

Fire Damage 158 

Fire Problems 127, 128 

Fire Island 37*, 39* 

Fireproofing of Buildings 121 

First Baptist Church, Oakland 136* 

Fissure and Landslip 8* 

Flagstaff Inn ..." 25 

Flood Building 145 

Cracking in 149* 

Formosan Earthquake ' . 316 

Comparison with California 296 

Fort Bragg 16 

Fort Ross 72, 102, 113, 293 

Fault Line at 105* 

Offset in Fence near 109* 

Pine Tree near 105* 

Redwood Tree near 105*, 103* 

Foundations 150 

Fracture Along Old Fault Line 263* 

Frame Buildings 128, 273 

Collapse of 127*, 129* 

Frawley Gulch 171 

Freeman's Ranch, Rift at 17*, 18* 

Gas Main Explosion 180* 

Geographic Changes ' 251 



[ 3 66 



Index to the California Earthquake of igo6 



PAGE 

Geological Effects : 279 

Geology and the Earthquake 63-77 

Gilbert, Grove K 213 

On Bogoslofs 49, 50 

Great Earthquake Rift 319, 322 

Great Fault, Course of 287* 

Guth Landing 278 

Half Moon Bay 278 

Hallock, Theory of Earthquakes 57 

Hall of Justice, San Jose 189* 

Hall of Records, San Jose 190* 

High Buildings 212 

Hinckley Gulch 29 

Hollister 92 

Hollow Tile 203 

Horizontal Shifting 250*, 324 

Hotel St. James, San Jose 305* 

Hotel Vendome, San Jose 191 

Inokuty 296 

Inverness Road 29* 

Investigations 220 

By Architects and Engineers 254 

By Japanese Government 223, 283 

By Structural Association 82 

California Earthquake 215 

Committees of 220 

Japan Earthquake of 1891 284 

Jefferson Square, View of 347 

Jordan, David 1 

King's Mountain House 275 

Kriukof, Account of Old Bogoslof 46 

Lafayette Square, View from 345* 

Lake Elizabeth 334 

Lake Merced .... 106 

Lake in Sunken Area 323* 

Landslips 8*, 247*, 238, 296 

At Sobrante 13*, 14* 

Lava Flow 6 

Lawson, Relief Map by 89* 

Library at Stanford University 309* 

Lime Mortar 204 

Live Oak Uprooted by Earthquake 74 

Local Effects 257 

Loma Prieta Sawmill 29, 30*, 31* 

Los Gatos Creek 27 

Loss of Life 307 

Main Coast Range Fault 91 



367] 



Index to the California Earthquake of igo6 



PAGE 

Manchester 294 

Map, of San Francisco Bay Region 159* 

Of California 3* 

Of San Francisco and Vicinity 89*, 287* 

Of Stevens Creek Fault 261* 

Showing Fault Line 217* 

Marshall Hotel 15*, 18 

Marshy Ground 235* 

Marysville Buttes 6 

Mediterranean Zone 316, 317 

Merriam and Mendenhall, on New Bogoslof 48 

Mills Building 139*, 212 

Milpitas, Slump in Soft Ground at 66* 

Monadnock Building 147 

Morrill Ranch 26*, 28* 

Moss Landing ._ 299 

Mount Tamalpais 303 

Mussel Rock 25, 69, 106, 325* 

Native Sons' Hall, San Jose 186* 

New Bogoslof 37*, 39*, 41* 

Cantwell on 47 

Merriam and Mendenhall on 48 

Rise f 47 44 

Nob Hill, View' After' Fire . ........... .351* 

North Shore Railroad 11* 18 

Train Overturned by Shock 21* 

Oak Tree Uprooted 74, 271*, 272 

Observatory on Strawberry Hill 308, 313* 

At Ukiah 253 

Ocean Shore Road 107 

Offset, Measure of Ill, 112 

Old Bogoslof 36*, 46 

Olema 22*, 23* 

Omori, F 223, 281 

Ordinary Frame Houses 128 

Owens Valley Earthquake 321 

Pajaro River Bridge 96, 108, 328 

First Intermediate Pier of 193* 

Shifting of 16 

West Abutment of 192* 

Palace Hotel 135 

Palmdale 334 

Palo Alto 180 

Parallel Faults 33 

Pescadero 279 

Physical Features of Earthquake 224 



[368 



Index to the C alif ornia Earthquake of igo6 



PAGE 

Pier at Inverness 293, 301 

Pilarcitos Conduit 96, 169 

Collapsed Trestle under 171, 175* 

Diagonal Rupture of 170*, 173*, 174* 

Telescoped Rupture 172* 

Pilarcitos Reservoir 161 

Pine Tree near Fort Ross 105* 

Point Arena 12* 

Point Arena Lighthouse 15 

Point Delgada 33 

Point Reyes Station 19, 106 

Portola-Tomales Fault 5, 8, 31, 259 

Portola Valley 26, 68, 266, 238 

Potato Canon 336 

Power-House of San Francisco Gas Company 138* 

Priest Valley . 31, 32 

Recent Seismic Activity 311 

Rectangular Framing 145 

Redwood Trees Snapped Off 273 

Redwood Snapped Off by Earthquake 72 

Redwood Tree near Fort Ross 103* 

Reinforced Concrete Buildings 141, 211 

Relief Map, of California 3* 

Of San Francisco Peninsula 89* 

Reservoirs 209 

Road Displacement, Tomales Bay 327* 

Ruptured Conveyor 199* 

Rupture of Car Tracks and Pavement 125*, 126* 

St. Francis Church 135* 

St. Francis Hotel 151* 

St. Patrick's Seminary 134 

Sail Rock 43 

Salinas Highway Bridge 194, 195 

Salt Water System 210 

San Andreas Fault 5, 228 

Dam 162, 164 

Lake 107, 111, 112* 

San Benito County .... 325 

San Bernardino Range 334, 335 

San Fernando Mountains 53 

San Francisco, Earthquake Effects in 120, 122 

And Vicinity, Map of 287 

On Night of Fire 342* 

Postoffice, Distortion and Subsidence of Sidewalk at . . 154* 

Peninsula, Relief Map of 89* 

San Jacinto Valley, Fissure in 8* 



[369 



Index to the Calif ornia Earthquake of igo6 



PAGE 

San Jose 188, 245 

First Street at 187* 

Hall of Justice at 189* 

Hall of Records 190* 

High School at 134* 

Native Sons' Hall at 186* 

San Juan 30, 328 

Santa Rosa 32, 113 

Carnegie Library at 115* 

Collapsed Court House Dome at 118* 

Destruction by Fire at 114, 119 

Effect of Earthquake at 118 

Flour Mill at 115* 

Frame Houses at 129* 

Scene in 117* 

Saratoga, House Located Over Rift at 70* 

School-House at Point Reyes 250* 

Sea Shock : 286 

Sea Waves > . '. 284 

Secondary Cracks 295 

Sewers and Water Pipes 124, 126* 

Shatter Ranch . . . 24 

Shearing Effect, Compression of 305* 

At Inverness 301 

Shearing Movements 294 

Shear of Ground 290 

Sketch Showing Course of Fault 291* 

Skinner's Ranch 20, 23* 

Slump in Soft Ground 66* 

Sobrante, Landslip at 13*, 14* 

Spreckels Sugar Mill 97, 196, 197* 

North Wall of 197 

Ruptured Conveyor at 199* 

West Wall of * 197* 

Stanford University 181, 276 

Arcade of 181* 

Arches at 277* 

Library Building at 309* 

Memorial Arch at 182*, 183*, 184 

State Earthquake Commission 219, 254, 255 

Steamer Argo 10, 286 

Steel Cable . 313 

Steel-Frame Brick House 309* 

Steel Columns 211 

Stevens Creek Fault, Map of 261* 

Stone Ornamentation 211 

Stone Structures 136 

Street Scene in San Francisco 239* 



[370] 



I 



Index to the Calif ornia Earthquake of igo6 



PAGE 

Street Surface, Showing Undulations 123* 

Structural Association of San Francisco, Investigation by . . . 82 

Surface Distortions, Examples of 124 

Taber, Stephen 257 

Tejon Earthquake 332, 337 

Tejon Pass . 333 

Telegraph Hill, View from, During Fire 343* 

Telescoped Rupture 172* 

Temblor 339 

Terra Cotta 150, 203 

Third Bogoslof, Gilbert, C. H., on 49 

Tidal Waves 285 

Time of Occurrence 284 

Time Observations 246 

Tivoli Theatre, View of 353 

Tomales Bay 15, 18, 289 

Tomales, Marin County 11* 

Topography and Geological Structure 95 

Train Overturned 21*, 19 

Trees, Injury to 241 

Triangular Framing '. . 144 

Typical Brick Structure 115* 

Ukiah, Observatory at 253 

Undulations and Cracks 123* 

Unalaska, Shocks at 50 

Valparaiso Earthquake 56, 315 

Van Ness Avenue, View on 347 

Vesuvius, Eruptions at . 316 

View on First Street, San Jose 187* 

Water Mains 208, 272 

Water Supply Disturbances 241 

Water Supply, Effect on 326 

Water Tanks 249*, 273 

Water Works Problems 176, 179 

Wave Motion 275 

Wooden Structures 117 

Woodside 268 

Wrights Tunnel 27, 108 



[371 ] 



DEC 18 190' 



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